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In this work, we compare labeling by two negatively charged fluorescent labels, 8-aminopyrene-1,3,6-trisulfonic acid (APTS) and 8-(2-hydrazino-2-oxoethoxy)pyrene-1,3,6-trisulfonic acid (Cascade Blue hydrazide [CBH]). Effectiveness of the labeling chemistries were investigated by 4-hydroxybenzaldehyde and maltoheptaose followed by LC/UV-MS and CE/LIF analysis, respectively. The reaction yield of APTS labeling was determined to be only ∼10%. This is due to reduction of almost 90% of the analyte by sodium cyanoborohydride to alcohol, which cannot be further labeled via reductive amination. However, the CBH labeling provides ∼90% reaction yield based on the LC/UV-MS measurements. The significantly higher labeling yield was also confirmed by CE/LIF measurements. Finally, the more effective hydrazone formation technique of CBH was characterized and applied for N-linked glycan analysis by CE/LIF.

2-Deoxyglucose (2-DG), an analog of glucose, is widely used to interfere with glycolysis in tumor cells and studied as a therapeutic approach in clinical trials. To evaluate the pharmacokinetics of 2-DG, we describe the development and validation of a sensitive HPLC fluorescent method for the quantitation of 2-DG in plasma. Plasma samples were deproteinized with methanol and the supernatant was dried at 45°C. The residues were dissolved in methanolic sodium acetate–boric acid solution. 2-DG and other monosaccharides were derivatized to 2-aminobenzoic acid derivatives in a single step in the presence of sodium cyanoborohydride at 80°C for 45 min. The analytes were separated on a YMC ODS C18 reversed-phase column using gradient elution. The excitation and emission wavelengths were set at 360 and 425 nm. The 2-DG calibration curves were linear over the range of 0.63–300 µg/mL with a limit of detection of 0.5 µg/mL. The assay provided satisfactory intra-day and inter-day precision with RSD less than 9.8%, and the accuracy ranged from 86.8 to 110.0%. The HPLC method is reproducible and suitable for the quantitation of 2-DG in plasma. The method was successfully applied to characterize the pharmacokinetics profile of 2-DG in patients with advanced solid tumors. Copyright © 2011 John Wiley & Sons, Ltd.

Analysis of N-glycans is often performed by LC coupled to fluorescence detection. The N-glycans are usually labeled by reductive amination with a fluorophore containing a primary amine to allow fluorescence detection. Moreover, many of the commonly applied labels also allow improved mass spectrometric detection of oligosaccharides. For reductive amination, the amine group of the label reacts with the reducing-end aldehyde group of the oligosaccharide to form a Schiff base, which is reduced to a secondary amine. Here, we propose the use of 2-picoline-borane as the reducing agent, as a non-toxic alternative to the extensively used, but toxic sodium cyanoborohydride. Using dextran oligosaccharides and plasma N-glycans, we demonstrate similar labeling efficacies for 2-picoline-borane and sodium cyanoborohydride. Therefore, 2-picoline-borane is a non-toxic alternative to sodium cyanoborohydride for the labeling of oligosaccharides.

Dimethylamine borane and trimethylamine borane were compared with sodium cyanoborohydride as reducing agents for the reductive methylation of amino groups in proteins. Dimethylamine borane performed nearly as well as cyanoborohydride; either reducing agent (15 mM) with 20 mM formaldehyde gave extensive methylation of turkey ovomucoid (5 mg/ml) in 2 h at 22 degrees. Trimethylamine borane gave equivalent levels of methylation only with a higher concentration of formaldehyde, suggesting that it is an even milder reducing agent than the other two under these conditions. With all three reducing agents, the pH optimum for methylation covered a range of pH 6-9. Methylations should be performed at the lowest possible pH to avoid side reactions of formaldehyde with the protein. Possible effects of these reducing agents on the disulfide bonds of proteins were studied. No reduction of disulfides of turkey ovomucoid was observed using each of the three reducing agents under conditions for methylation.

Primary amino groups on the model peptide Xaa-Ala-Pro-Lys(ClZ)-Tyr(2BrZ), synthesized on a p-methylbenzhydryl amine resin with conventional Boc/benzyl protective group strategy, were reacted with 4,4'-dimethoxydityl chloride in dichloromethane, resulting in the introduction of the dimethoxydityl group, which is an acid-labile N-alkyl type of protective group. The secondary amino groups thereby formed can be methylated by treating the peptide-resin with formaldehyde and sodium cyanoborohydride in N,N-dimethylformamide. After the removal of the dimethoxydityl group with trifluoroacetic acid, the resulting N-methylated amino acid residues with a free secondary amino groups are accessible for acylation with the next activated Boc amino acid. With this method majority of the 20 common amino acids can be monomethylated directly on the resin and, in most cases, with very low levels of the side reactions. In the cases where the complete methylation is difficult to achieve, the remaining primary amino groups can be selectively acylated in the presence of secondary amino groups with trimethylacetic acid 1-hydroxybenzotriazole ester. The method provides a convenient general route to synthesize N-methylated derivatives of most of the occurring and synthetic amino acids.

Lewis acid promoted rearrangements of different 4-alkoxy-substituted 1,2-oxazines syn-1 are reported. Depending on the nature of this alkoxy group different reaction pathways are possible either providing bicyclic 1,2-oxazinones 2 or the novel tricyclic products 3–5. A mechanistic rational describing the role of the 4-alkoxy group is presented. The key step for formation of tricyclic skeletons 3–5 is a 1,2-alkyl shift. Hydrogenation reactions of these tricyclic compounds gave unsaturated 1,2-oxazines 12 and 13 or tetrahydrofurans 15a–c/16a–c depending on the time of hydrogenolysis. Tetrahydrofuryl-annulated 1,2-oxazine 12 was used for further transformations into complex substituted tetrahydrofurans. Reduction with sodium cyanoborohydride and subsequent cleavage of the N,O-bond by hydrogenation furnished aminofuran derivative 19. Alternatively treatment with a strong base such as n-butyllithium afforded imidoester 21 via a Beckmann-type fragmentation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

C-Terminal peptide aldehydes and hydroxamates comprise two separate classes of effective inhibitors of a number of serine, aspartate, cysteine, and metalloproteases. Presented here is a method for preparation of both classes of peptide derivatives from the same resin-bound Weinreb amide precursor. Thus, 5-[(2 or 4)-formyl-3,5-dimethoxyphenoxy]butyramido-polyethylene glycol-polystyrene (BAL-PEG-PS) was treated with methoxylamine hydrochloride in the presence of sodium cyanoborohydride to provide a resin-bound methoxylamine, which was efficiently acylated by different Fmoc-amino acids upon bromo-tris-pyrrolidone-phosphonium hexafluorophosphate (PyBrOP) activation. Solid-phase chain elongation gave backbone amide-linked (BAL) peptide Weinreb amides, which were cleaved either by trifluoroacetic acid (TFA) in the presence of scavengers to provide the corresponding peptide hydroxamates, or by lithium aluminum hydride in tetrahydrofuran (THF) to provide the corresponding C-terminal peptide aldehydes. With several model sequences, peptide hydroxamates were obtained in crude yields of 68-83% and initial purities of at least 85%, whereas peptide aldehydes were obtained in crude yields of 16-53% and initial purities in the range of 30-40%. Under the LiAlH4 cleavage conditions used, those model peptides containing t-Bu-protected aspartate residues underwent partial side chain reduction to the corresponding homoserine-containing peptides. Similar results were obtained when working with high-load aminomethyl-polystyrene, suggesting that this chemistry will be generally applicable to a range of supporting materials.

This paper describes the structural elucidation of a compound produced during the synthesis of 3,4-methylenedioxymethylamphetamine (MDMA) via the reductive amination of 3,4-methylenedioxyphenyl-2-propanone (3,4-MDP-2-P) with methylamine and sodium cyanoborohydride. The compound was isolated from MDMA by column chromatography, proton and carbon nuclear magnetic resonance spectroscopy, LC/mass spectrometry, and total synthesis were used to identify the compound as N-cyanomethyl-N-methyl-1-(3′,4′-methylenedioxyphenyl)-2-propylamine. This compound has been identified as a potential synthetic route marker for the reductive amination of 3,4-MDP-2-P with methylamine and sodium cyanoborohydride and as such it should prove valuable to forensic scientists engaged in profiling illicit drugs. Profiling MDMA can provide useful information to law enforcement agencies relating to synthetic route, precursor chemicals and reagents employed and may be used for comparative analyses of different drug seizures. This paper also describes the structural elucidation of the analogous methylamphetamine synthetic route marker compound, N-cyanomethyl-N-methyl-1-phenyl-2-propylamine, produced during the reductive amination of phenyl-2-propanone using methylamine and sodium cyanoborohydride.

A tandem reductive amination-SNAr reaction has been developed for the synthesis of 6-nitro-1,2,3,4-tetrahydroquinolines. Treatment of 4-(2-fluoro-5-nitrophenyl)-2-butanone or 3-(2-fluoro-5-nitrophenyl)-propanal with primary amines and sodium cyanoborohydride in methanol at room temperature provided good to excellent yields of the substituted tetrahydroquinolines. The reaction proceeded best with the ketone substrate using primary amines that were unbranched at the α-carbon. The aldehyde also produced the target heterocycles, but these were accompanied by 10-15% of the uncyclized side chain reductive amination products.

β-Amylase was coupled to a periodate oxidized dextran by reductive alkylation in the presence of sodium cyanoborohydride. The loss of activity (57%) during the cross-linking of the enzyme was the result of steric hindrance near the catalytic site. In order to verify this hypothesis, the residual activity was determined with substrates of variable molecular size. The residual activity was inversely proportional to the particulate size of the substrate. Increases in residual activity, of up to 53% were obtained using an orientated chemical modification in the presence of a substrate which protects the catalytic site. Native and dextran-conjugated β-amylase were immobilized on an amino activated silica by a classical method using glutaraldehyde for the native enzyme and by reductive alkylation for the modified enzyme. The relative activity of the enzymes obtained after this insolubilization was very high for the modified amylase, 45% for a medium enzyme concentration, compared with 4% at the same concentration for the native enzyme. This difference can be attributed to the variation of the length of the space arm between the silica and the enzyme. The soluble β-amylase dextran conjugate had a superior thermoresistance to that of the native enzyme; its optimal temperature of activity was 5°C higher than that of the native enzyme. This stabilization may be attributable to a rigidification of the protein structure. Immobilization of both native and modified enzymes on a amino silica resulted in thermostabilization of the enzymes. The optimal temperature of activity was 70°C for the native immobilized β-amylase (some 10°C higher than that of the native enzyme) and 75°C for the chemically modified, and subsequently immobilized, β-amylase. The immobilized forms of the enzymes were used for 14 days at 55°C in continuous substrate processing. The greater eflciency of the chemically modified β-amylase was demonstrated by a four-fold increase in maltose production compared to the classical method of immobilization. A kinetic study confirmed the stabilization of the β-amylase by a reduction of the rate constant of inactivation of the different modified enzymes.

Stable-isotope labeling coupled with liquid-phase separation and MS analysis is a powerful technique for comparative proteomics. We developed a dimethyl labeling strategy (Anal. Chem. 2003, 75, 6843-6852 and J. Proteome Res. 2005, 4, 101-108) to label peptide N-terminus and epsilon-amino groups of Lys with water-soluble formaldehyde via reductive methylation, and an isotopic pair of formaldehyde is used for binary labeling on two sets of samples. In this study, this approach is extended to a four sample labeling by combining the binary isotopic reagents of formaldehyde (d0, d2) and the binary isotopic reducing reagents, sodium cyanoborohydride (d0, d3). To ensure sufficient mass difference, this multiplexed labeling is coupled with endoproteinase Lys-C instead of trypsin for digestion, resulting in at least two labeling sites with a mass difference of 4 Da for each pair of peptide digest. Moreover, multiplex dimethyl labeling was proved to have no significant isotopic effect during RP LC elution. This method was further applied for monitoring Lys-C digestion using hemoglobin as a model. Dimethyl labeled digests derived from seven time points (1-30 h) were grouped into two sets of sample mixtures, separated by nano-LC to reduce the complexity, and then analyzed by ESI-MS/MS. The temporal study reveals that Lys-C digestion was completed in 10-15 h for all detected peptides. The multiplex dimethyl method has not only provided a simultaneous detection mean for four sample sets but has also conserved all the advantages associated with the original binary method.

The synthesis of 1-(5-chloro-2-{2-[(2R)-4-(4-[18F]fluorobenzyl)-2-methylpiperazin-1-yl]-2-oxoethoxy}phenyl)urea ([18F]4), a potent nonpeptide CCR1 antagonist, is described as a module-assisted two-step one-pot procedure. The final product was obtained utilizing the reductive amination of the formed 4-[18F]fluorobenzaldehyde (2) with a piperazine derivative 3 and sodium cyanoborohydride. After HPLC purification of the final product [18F]4, its solid phase extraction, formulation and sterile filtration, the isolated (not decay-corrected) radiochemical yields of [18F]4 were between 7 and 13% (n=28). The time of the entire manufacturing process did not exceed 95 min. The radiochemical purity of [18F]4 was higher than 95%, the chemical purity ⩾60% and the enantiomeric purity >99.5%. The specific radioactivity was in the range of 59–226 GBq/µmol at starting radioactivities of 23.6–65.0 GBq [18F]fluoride. Copyright © 2006 John Wiley & Sons, Ltd.

New functionalized carboranyl derivatives of amineboranes and boron analogs of esters are reported. The reaction of 1,12-(aminopropyl)-1,12-dicarbadodecaborane (2), 2-(aminopropyl)-1,2-dicarbadodecaborane (4), 1-methyl-2-(aminopropyl)-1,2-dicarbadodecaborane (6), 1-phenyl-2-(aminopropyl)-1,2-dicarbadodecaborane (8) with Me 3 NBH 2 X produced novel carboranylamineboranes of the general formula 1,12-[(CH 2 ) 3 NH 2 BH 2 X] 2 -1,12-C 2 B 10 H 10 [X = CN (2a), COOCH 3 (2b), CONHEt (2c), CONHCH(CH 2 C 6 H 5 )COOCH 3 (2d), CONHCH(CH 3 )COOCH 3 (2e), CONHCH[CH(CH 3 ) 2 ]COOCH 3 (2f), CONHCH(CH 2 C 6 H 4 OH)COOCH 3 (2g), 1-CH 2 NH 2 BH 2 CN (2h)] or 1-R-2-[(CH 2 ) 3 NH 2 BH 2 X]-1,2-C 2 B 10 H 10 {R = H, X = CN (4a), COOCH 3 (4b), CONHEt (4c), COOH (4d); R = CH 3 , X = CN (6a), COOCH 3 (6b), CONHCH(CH 2 C 6 H 5 )COOCH 3 (6c), CONHCH(CH 3 )COOCH 3 , (6d), CONHCH[CH(CH 3 ) 2 ]COOCH 3 (6e), CONHCH(CH 2 C 6 H 4 OH) COOCH 3 (6f); R = C 6 H 5 , X = CN (8a), COOCH 3 (8b), CONHCH(CH 2 C 6 H 5 )COOCH 3 (8c), CONHCH(CH 3 )COOCH 3 (8d), CONHCH[CH(CH 3 ) 2 ]COOCH 3 (8e), CONHCH(CH 2 C 6 H 4 OH) COOCH 3 (8f)) by the amine exchange reaction. The reaction of 1-(aminomethyl)-1,2-dicarbadodecaborane with Me 3 NBH 2 X (X = CN) produced 1-[CH 2 NH 2 BH 2 CN]-1,2-C 2 B 10 H 10 (2h). Compounds 2a, 4a, 6a, and 8a were also synthesized by the reaction of 1,12-(aminopropyl)-1,12-dicarbadodecaborane hydrochloride (1), 2-(aminopropyl)-1,2-dicarbadodecaborane hydrochloride (3), 1-methyl-2-(aminopropyl)-1,2-dicarbadodecaborane hydrochloride (5), 1-phenyl-2-(aminopropyl)-1,2-dicarbadodecaborane hydrochloride (7) with sodium cyanoborohydride. The reaction of Li 2 [1,2-CO 2 -1,2-C 2 B 10 H 10 ] (9) or Li[1-R-2-CO 2 -1,2-C 2 B 10 H 10 ], R = CH 3 (10), R = C 6 H 5 (11), with Me 3 NBH 2 I gave 1,2-CO 2 BH 2 NMe 3 -1,2-C 2 B 10 H 10 (9a) or 1-R-2-CO 2 BH 2 NMe 3 -1,2-C 2 B 10 H 10 , R = CH 3 (10a), R = C 6 H 5 (lla), as new boron analogs of esters. All of these compounds were characterized by IR spectroscopy, 1 H, 13 C and 11 B NMR spectroscopy and chemical analyses.

A modified polysulfone containing benzylamine groups was synthesized as a reactive membrane material. Polysulfone was activated at the ortho-sulfone site by direct lithiation with n-butyllithium, and the resulting lithiated polysulfone was then reacted with benzonitrile; this yielded a polymer with pendant benzimine groups. The structure was confirmed by NMR and IR spectroscopy and by the transformation of imine to ketone by acid hydrolysis. The polymeric benzimine was also reduced to benzylamine with sodium cyanoborohydride in an acidic medium. The structure and degree of substitution of both benzylamine derivatives were determined by NMR and IR spectroscopy. The modified polysulfone containing benzylamine groups initiated the polymerization of N-carboxyanhydride of γ-benzyl-L-glutamate [Glu(OBzl)–NCA]. The side-chain oligopeptide of Glu(OBzl)–NCA attached to polysulfone was converted into molecular recognition sites. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1316–1329, 2003

A set of 11 each of 2,4,6-triphenylpyrylium, -thiopyrylium and -N-methylpyridinium tetrafluoroborates carrying a range of substituents in the phenyl rings were prepared. First and second wave reduction potentials were determined. For the thiopyrylium series there are linear correlations between scaled potentials (E°/0.05915) and summed Hammett constants for substituents in the pendant phenyl groups (σ = 2.29 and 3.38 for first and second waves respectively). For the pyrylium series, a good linear relationship (σ = 2.79) is obtained for all substituent patterns for the first wave reduction potentials, but for the second wave there are separate correlations for salts carrying substituents in the 4-phenyl and for those carrying substituents in 2- and 6-phenyls. For the pyridinium series, the first wave potentials show separate correlations for salts carrying substituents in the 4-phenyl and for those carrying substituents in 2-and 6-phenyls, but a single linear relationship for the second wave potentials. These are related to particular structural features in the cations, radicals and anions in each series. Rates and products were determined for reductions of the pyrylium and thiopyrylium cations by sodium cyanoborohydride and of all cations by sodium borohydride in acetonitrile solution. Reactions are first order in reducing agent and cation. Primary kinetic isotope effects were determined for borohydride reduction of the least reactive of each of the series of cations. Plots of logarithms of second-order rate constants against summed Hammett constants for substituents in the pendant phenyl groups are linear for all combinations of reagent and cation with 0.91 < σ < 1.50 across all substituent patterns. For parent pyrylium and thiopyryliums, kBH4/kCNBH3 = 8.4 × 104 and 1.5 × 104, respectively, and for reductions by borohydride the reactivities of the pyrylium, thiopyrylium and pyridinium, series decrease in the order 1.4 × 105:8.8 × 103:1. Constant selectivities are not observed. Comparison of the correlations for electrochemical reduction and for hydride addition leads to the conclusion that charge neutralization in the hydride addition transition states runs ahead of bonding changes at the originating B—H bond. Copyright © 2002 John Wiley & Sons, Ltd.

During the total synthesis of calothrixin B, various novel and unexpected results were noticed such as cleavage of C–N bond in imine using sodium cyanoborohydride, sodium methoxide as a hydride source for reduction, deformylation in the presence of bromine, and deacylation using ceric ammonium nitrate (CAN). A detailed mechanism has been proposed for the unexpected results and a few of them are generalized. Temperature dependent NMR studies have been carried out for confirmation of the structure of one of the intermediates in the synthetic sequence.

The synthesis of 6-chloro-9-nitro-benzothiopyranopyridin-5-ones 2a, 2b and 2c has been accomplished. Chemotype 2d could not be prepared since attempts to cyclize 3-(2-nitro-5-chlorophenoxy)pyridine-2-carboxylic acid (1d) led to the decarboxylation product 3-(2-nitro-5-chlorothiophenoxy) pyridine (40). Analogues 2a, 2b or 2c on treatment with the respectively substituted hydrazine led to the 2-(substituted)-5-nitro 7, 8- or 9-aza substituted chemotypes 3a-7a, 8b, and 9c-13c. The reduction of the nitro groups of these substrates was effected by treatment with hydrogen gas (palladium catalyst) or by stannous chloride to yield the 5-amino chemotypes 15a-18a, 20b and 21c-24c, respectively. The conversion of these derivatives to the 2,5-bis (alkylamino)-7-, 8- and 9-aza benzothiopyranoindazoles listed in Table 3 was accomplished by direct alkylations, acylations, followed by reduction of the amido group with Red-Al or lithium aluminum hydride, or by reductive alkylations in the presence of sodium cyanoborohydride. The removal of the protective BOC-group was effected by treatment of the appropriate substrates with anhydrous hydrogen chloride to afford the respective hydrochloride salts listed in Table 4.

The synthesis of 15 N-labelled nornicotine 2 and 15 N-labelled nicotine 1 is described via the reductive aminocyclization of a 1,4-ketoaldehyde with a corresponding amine in the presence of sodium cyanoborohydride. Yields of 30% and 26%, respectively, were obtained from 3-bromopyridine. The 15 N-label has been easily introduced from ammonium- 15 N-labelled chloride as an inexpensive label source. As far as we are aware, this is the first synthesis of 15 N-labelled nicotine.

2-Pyridin-3-ylbenzoxazoles were synthesized by the reaction between 3-pyridinecarboxaldehyde and substituted o-aminophenols in the presence of iodobenzene diacetate. The resulting benzoxazoles 3 were treated with methyl iodide to give the corresponding pyridinium salts 4 which underwent the hydride reduction with sodium borohydride or sodium cyanoborohydride to produce 2-(1-methyl-1,2,5,6-tetrahy-dropyridin-3-yl)benzoxazole borane complex derivatives.

Fluorine-18 labeled norchlorofluoroepibatidine (NFEP), a high-affinity nicotinic acetylcholine receptor ligand, was prepared by a one-pot, two-step synthesis: nucleophilic heteroaromatic substitution of a tert-Boc protected precursor (7-tert-butyloxycarbonyl-exo-2-(2'-N,N,N-trimethylammonium-5'-pyridinyl)-7-azabicydo[2.2.1]heptane iodide) using no-carrier-added [ 18 F]fluoride followed by deprotection with trifluoroacetic acid. Subsequent reductive N-methylation with formaldehyde and sodium cyanoborohydride afforded fluorine-18 labeled N-methyl-norchlorofluoroepibatidine (N-methyl-NFEP). The unusually high radiochemical yield for the first step (70%) and the quantitative conversions in the deprotection and N-methylation steps afforded overall radiochemical yields of 55-65% (decay corrected based on starting [ 18 F]fluoride) for [ 18 F]NFEP (synthesis time 65 min) and 45-55% for [ 18 F]N-methyl-NFEP (synthesis time 75 min), with a specific activity of 2-9 Ci/μmole (EOB).

We have prepared Schiff base adducts of the core aldehydes of phosphatidylcholine and aminophospholipids, free amino acids, and myoglobin. The Schiff bases of the ethanolamine and serine glycerophospholipids were obtained by reacting sn-1-palmitoyl(stearoyl)-2-[9-oxo]nonanoyl-glycerophosphocholine (PC-Ald) with a twofold excess of the aminophospholipid in chloroform/methanol 2:1 (vol/vol) for 18 h at room temperature. The Schiff bases of the amino acids and myoglobin were obtained by reacting the aldehyde with an excess of isoleucine, valine, lysine, methyl ester lysine and myoglobin in aqueous methanol for 18 h at room temperature. Prior to isolation, the Schiff bases were reduced with sodium cyanoborohydride in methanol for 30 min at 4 degrees C. The reaction products were characterized by normal-phase high-performance liquid chromatography and on-line mass spectrometry with electrospray ionization. The amino acids and aminophospholipids yielded single adducts. A double adduct was obtained for myoglobin, which theoretically could have accepted up to 23 PC-Ald groups. The yields of the products ranged from 12 to 44% for the aminophospholipids and from 15-57% for the amino acids, while the Schiff base of the myoglobin was estimated at 5% level. The new compounds are used as reference standards for the detection of high molecular weight Schiff bases in lipid extracts of natural products.

Upon reaction of 4,5-disubstituted-N-arylaminoimidazole-2-thiones with isocyanides in the presence of azodicarboxylates (1.2 equiv) at rt, the imidazo[2,1-b][1,3,4]thiadiazoles were formed as the only reaction products in very good yields, whereas by using higher reaction temperatures, along with the imidazo[2,1-b][1,3,4]thiadiazoles, the three component reaction products, namely thiadiazoles, were also isolated, their formation being dependent on the 5-thione substituent. The thiadiazoles became the only reaction products, formed in very good yield by using 2 equiv of azodicarboxylates. The sodium cyanoborohydride and sodium borohydride reductions to thiadiazoles 11, and 12 were also studied. Plausible mechanistic schemes for the formation of the thiadiazoles are proposed.

(R)-α-Aminoadipic acid is a readily available enantiomerically pure starting material for the synthesis of (R)-pipecolic acid and its derivatives. Sonogashira or Suzuki cross-coupling reactions of an N-formyl pipecolate-derived vinyl bromide furnish 6-alkynyl or aryl derivatives. Reduction with sodium cyanoborohydride and subsequent N-deformylation provide 6-alkynyl substituted (R)-pipecolic acid derivatives, valuable building blocks for amino acid and peptide chemistry.

trans-α-Alkoxy-β-halotetrahydropyridines are synthesized in a very efficient single step by stereocontrolled N-halosuccinimide (NXS)–promoted alcohol addition to the enamine group in N-alkyl-1,4-dihydropyridines. These compounds are cyclized using sodium cyanoborohydride in the presence of 2,2′-azobis(2-methylpropionitrile), azabisisobutyronitrile (AIBN) (cat.), and tributylstannane (cat.), affording hexahydrofuro[2,3-b]pyridine and hexahydropyrano[2,3-b]pyridine derivatives. The cyclized product undergoes ring-opening reaction by a nucleophile in the presence of Lewis acid to afford highly functionalized tetrahydropyridines.

(2S,3R)-2-[3-(4-Fluorophenyl)]propylamino-3-(3,4-dihydroxyphenyl)-3-hydroxypropionic acid pyrrolidine amide hydrobromide (SM-11044) was labeled with carbon-14 for use in mammalian metabolic studies. The synthesis was achieved according to the scheme shown in Fig. 5. Grignard reaction of 3,4-methylenedioxy-phenylmagnesium bromide with [14C]carbon dioxide liberated from barium [14C]carbonate ((UNDERLINE)6(/UNDERLINE)) gave the acid ((UNDERLINE)5(/UNDERLINE)). Reduction of (UNDERLINE)5(/UNDERLINE) with lithium aluminum hydride followed by oxidation of the resulting benzyl alcohol ((UNDERLINE)11(/UNDERLINE)) with chromium oxide-pyridine complex afforded the aldehyde ((UNDERLINE)3(/UNDERLINE)). Condensation of (UNDERLINE)3(/UNDERLINE) with the optically active (R)-oxazolidinone ((UNDERLINE)10(/UNDERLINE)) yielded the alcohol ((UNDERLINE)12(/UNDERLINE)). Catalytic hydrogenation of (UNDERLINE)12(/UNDERLINE) and subsequent hydrolysis produced the optically active β-hydroxy-α-amino acid ((UNDERLINE)2(/UNDERLINE)), which was treated with N-carbomethoxyphthalimide to give the hydroxy acid ((UNDERLINE)13(/UNDERLINE)). Reaction of (UNDERLINE)13(/UNDERLINE) with pivaloyl chloride gave the corresponding mixed anhydride, which was allowed to react with pyrrolidine to provide the amide ((UNDERLINE)14(/UNDERLINE)). Deprotection of (UNDERLINE)14(/UNDERLINE) with hydrazine hydrate afforded the hydroxyamide (15). Condensation of (UNDERLINE)15(/UNDERLINE) with the aldehyde ((UNDERLINE)16(/UNDERLINE)) and subsequent reduction of the resulting imine with sodium cyanoborohydride produced the fluoride ((UNDERLINE)17(/UNDERLINE)). Cleavage of the methylenedioxy group of (UNDERLINE)17(/UNDERLINE) gave the free base of (UNDERLINE)1(/UNDERLINE), which was treated with hydrobromic acid to afford (UNDERLINE)1(/UNDERLINE). The overall yield was 11.1% from (UNDERLINE)6(/UNDERLINE).

4-Amino[7-14C]benzoic acid (3) is prepared by carbonation of the lithium salt of N,N-bis(trimethylsilyl)aniline. The methyl ester (4) of 3 is generated with trimethylsilyldiazomethane, and 4 is coupled with 2,5-dihydroxybenzaldehyde to yield methyl 4-(2,5-dihydroxy-benzylimino)[7- 14 C]benzoate (5). 5 is reduced with sodium cyanoborohydride to give methyl 4-(2,5-dihydroxybenzylamino)[7- 14 C]-benzoate with a specific activity of 38.9 mCi/mmol. Unlabeled 5 is reduced with tritium gas to give methyl 4-(2,5-dihydroxy[7- 3 H]-benzylamino)benzoate with specific activity of 7.6 Ci/mmol.

A simple procedure is described for preparing 125I-labelling hyaluronan of high molecular weight. The reducing terminal group of hyaluronic acid was derivatized with tyramine through the formation of a Schiff base which was subsequently reduced with sodium cyanoborohydride. By radioiodination of the aromatic ring, 125I-labelled hyaluronic acid was obtained in high yield (40%) and high specific activity, 555 GBq/mmol (15 Ci/mmol).

An exceptional oxidizing behavior of sodium cyanoborohydride is observed where electron-withdrawing heterocyclic aldehydes are directly converted to their corresponding esters.

During the past decades, sodium borohydride has played an important role for the reduction of functional groups in modern organic synthesis. This reagent is a relatively mild reducing agent and mostly used for the reduction of aldehydes and ketones in protic solvents. In order to control the reducing power of NaBH4, hundreds of substituted boron hydrides have been made and introduced in chemical literature and many of them are now commercially available. In fact, advances in such field have been realized by replacement of one or more hydride with other substituents, change of sodium cation to other metal, quaternary ammonium and phosphonium cations, a concurrent cation and hydride exchange, ligand metal borohydrides and finally combination of the hydride transferring agents with metals, metal salts, Lewis acids and solid supports. In this context, NaBH3CN carrying an electron withdrawing cyanide group is a remarkable stable and selective reducing agent and has been found many applications in organic synthesis. It is also well known that the reducing capability of NaBH3CN in reduction reactions is greatly depended to use low pH values (3-4). In spite of the great convenience of NaBH3CN in synthetic organic chemistry, however, this reagent suffers from harsh reaction conditions (strongly acidic media), limitation to use acid-sensitive functional groups and formation of some side products. In line of the outlined strategies and our research interest to develop mild and efficient protocols for sodium cyanoborohydride reduction of functional groups in the absence of Bronsted acidic media, herein, we wish to introduce a new and convenient method for reduction of various aldoximes and ketoximes to their corresponding amines with NaBH3CN/ MoCl5/NaHSO4·H2O system in refluxing EtOH or DMF (Scheme 1). Results and Discussion

When soy isolate was mixed with sodium alginate, the two polymers interacted to form electrostatic complexes. They also formed varying degrees of covalent bonding, depending on reaction time and the presence or absence of the reducing agent sodium cyanoborohydride. On the other hand, soy isolate and propyleneglycol alginate (PGA) formed mostly covalent complexes at alkaline pH. The interaction of soy protein with polysaccharide maintained or improved its solubility and emulsifying activity, particularly when covalent bonds were involved. The alkylated complexes also showed better film-making properties. However, protein-PGA films were more readily formed and had greater stability in water than the protein-alginate films.

Starting from 7-alkoxy-4-aminocoumarins 5,6,8,12, and 13 as key intermediates, this paper describes two different methods for the preparation of azacannabinoidal 5H[1]benzopyrano[4,3-b]pyridin-5-ones 24–27, 38, and 39 containing typical structural requirements for ZNS activity. First, Michael addition of 6 and 8 to the double bonds of alkyl vinyl ketones 14 and 15 resulted in a mixture of tetrahydropyridines 24–27 and fused pyridines 20–23 the latter of which were reduced by sodium cyanoborohydride to give the target compounds 24–27. The second, pyridine ring closure was accomplished by a combination of Vilsmeier acetylation and formylation resulting in fused 4-chloropyridines 31–33 followed by reduction.

A simple procedure is described for preparing125I-labelled alginic acid. The reducing terminal of alginic acid is derivatized with tyramine through the formation of Schiff base which is subsequently reduced with sodium cyanoborohydride. By radioiodination of the aromatic ring introduced,125I-labelled alginic acid was obtained with high specific activity.

Amino analogues of cholic acid have been synthesized by reduction of the corresponding oximes with titanium(iii) chloride in the presence of sodium cyanoborohydride.

Treatment of the hydrochloride salts of 4-chloro-5-(2-halomethylaryl-imino)-5H-1,2,3-dithiazoles (2) with sodium cyanoborohydride in THF at room temperature gave 2-cyano-4H-3,1-benzothiazines (1) in good to moderate yields. 2-Cyano-4H-3,1-benzoxazines (4) were obtained in good to moderate yields by refluxing of 4-chloro-5-(2-hydroxymethylarylimino)-5H-1,2,3-dithiazoles (3) with sodium hydride in THF. Intermolecular reaction of 5-(p-tolylimino)-5H-1,2,3-dithiazole (12) with benzyl alcohol under the same conditions gave the acyclic analog of 4.

The reaction mentioned in the title converts the N-phenylsulfonylindols (I) to the corresponding indolines (II).

The potassium salt 2 of 1,3,3-trimethyl-N-nitro-2-oxabicyclo[2.2.2]octan-6-imine 1 reacted with bromine in acetic acid solution to give (1S,4S,5S)-5-bromo-1,3,3-trimethyl-N-nitro-2-oxa-bicyclo[2.2.2]octan-6-imine 3. Bromination of the salt 2 in methanolic potassium hydroxide afforded a mixture of (1S,4S)-5,5-dibromo-1,3,3-trimethyl-N-nitro-2-oxabicyclo[2.2.2]octan-6E-and -6Z-imine 4 and 5, whose X-ray crystal-structure determinations allowed their absolute configurations to be established. Bromination of monobromide 3 under different conditions gave the dibromide 4, which was converted into isomer 5 by storage in chloroform solution. Nitrimine 3 reacted with hydroxylamine hydrochloride and sodium hydroxide or piperidine to give (1S,4S,5S)-5-bromo- and -5-hydroxyamino-N-hydroxy-1,3,3-trimethyl-2-oxabicyclo[2.2.2]octan-6-imine or (1S,4S,5S)-N-hydroxy-1,3,3-trimethyl-5-(piperidin-1-yl)-2-oxabicyclo[2.2.2]octan-6-imine. Reaction of compound 3 with aliphatic and aromatic primary amines afforded N-substituted (1S,4S,5S)-5-bromo-1,3,3-trimethyl-2-oxabicyclo[2.2.2]octan-6-imines. Reduction of compound 3 with sodium cyanoborohydride gave (1S,4S,5S)-5-bromo-1,3,3-trimethyl-N-mtro-2-oxabicyclo[2.2.2]octan-6-amine, whereas consecutive treatment with potassium hydroxide and aq. hydrochloric acid afforded the less stable isomer (1S,4S)-5-bromo-1,3,3-trimethyl-N-nitro-2-oxabicyclo[2.2.2]oct-5-en-6-amine.

Unsaturated hydroperoxides (R1R2CHO2H), 2-phenylpent-4-enyl hydroperoxide (1), 3-phenylhex-5-en-2-yl hydroperoxide (2), 5-methylhex-5-en-2-yl hydroperoxide (3), cyclo-oct-4-enyl hydroperoxide (18), and cyclo-oct-3-enyl hydroperoxide (24) have each been prepared from the corresponding carbonyl compound (R1R2CO) by the sequence: i, conversion to the p-tosylhydrazone (R1R2CN–NHTs); ii, reduction with sodium cyanoborohydride at pH 3.5 to give the N′-p-tosylhydrazine (R1R2CH–NH–NHTs); and iii, oxidation with hydrogen peroxide and sodium peroxide, Isomerisation occurs in the preparation of the cyclo-octenyl hydroperoxides, particuarly if the pH falls markedly below 3.5 in the reduction step.

(Benzyloxycarbonyl)- and (tert-butoxycarbonyl)hydrazones are easily reduced by sodium cyanoborohydride in acidic medium. The method is an alternative to catalytic hydrogenation and allows ready access to both N-benzyloxycarbonyl and N-tert-butoxycarbonyl protected N'-alkyl- and N'-arylmethylhydrazines. The products can be isolated as the solid, stable cyanoborane adducts

A regioselective synthesis of 8,9-dichloro-2,3,4,5-tetrahydro-1H-2-benzazepine (LY134046, 10) and its 3-methyl analogue 26 from 6,7-dichloro-3-hydroxyphthalide (16) is described. The key step involved 1,4-hydride addition to the α,β-unsaturated nitrile 17 to give the saturated nitrile 18 using sodium borohydride in 2-propanol. In the preparation of LY134046 10, the COOH group in 18 was first esterified and then the nitrile function was selectively reduced with borane to yield the aminoester 20. The aminoester 20 was then cyclized to the azepinone 21 which on reduction with borane provided LY134046 10 in an overall yield of 22%. The route is adaptable to the preparation of hitherto unknown 3-substituted-2-benzazepines as demonstrated by the preparation of the 3-methyl analogue 26. In this case the nitrile 18 was reacted with an excess methylmagnesium iodide to give the ketoacid 22. Esterification of 22 followed by reductive amination with sodium cyanoborohydride and ammonium acetate provided the aminoester 24, which was then converted to the target benzazepine 26 as described earlier for the title compound. The reaction conditions and the reagents used throughout the sequence are fairly mild and many functional groups may be tolerated. The only limitation to this procedure is the availability of the corresponding hydroxyphthalide. A variation in the choice of reagent in the Grignard reaction of 18 should provide an access to a variety of 3-substituted-2-benzazepines.

Reactions of several substituted 1H-4,5-dihydroimidazolium salts 1 with nucleophilic and electrophilic reducing agents acting via hydride transfer were explored. Reaction of compounds 1 with lithium aluminum hydride in THF afforded the corresponding imidazolidines 2. When alkaline borohydrides (sodium borohydride, potassium borohydride, sodium cyanoborohydride) in ethanol at room temperature were used, partial or total over-reduction of compounds 2 leading to N,N,N'-trisubstituted ethylenediamines took place on occasion. Results may be explained taking into account that reductive cleavage of 2 proceeds via a stabilized iminium ion present in protic solvents. Treatment of compounds 1 with an excess of borane in THF afforded the corresponding imidazolidines 2 or their borane complexes, according to the substituent type.

Treatment of the hydrochloride salts of 4-chloro-5-(2-halomethylaryl-imino)-5H-1,2,3-dithiazoles (2) with sodium cyanoborohydride in THF at room temperature gave 2-cyano-4H-3,1-benzothiazines (1) in good to moderate yields. 2-Cyano-4H-3,1-benzoxazines (4) were obtained in good to moderate yields by refluxing of 4-chloro-5-(2-hydroxymethylarylimino)-5H-1,2,3-dithiazoles (3) with sodium hydride in THF. Intermolecular reaction of 5-(p-tolylimino)-5H-1,2,3-dithiazole (12) with benzyl alcohol under the same conditions gave the acyclic analog of 4.

The synthesis of various allyl glycosides of L-rhamnose containing ether and/or ester substituents are reported. Ozonolysis of allyl glycosides followed by reductive amination with ∊-amino groups of lysine residues in bovine serum albumin using sodium cyanoborohydride at pH 7.8 provided different structural neoglycoproteins as artificial antigens.

The one-pot preparation of hindered 1,2-diarylethylamines 3 and 4 and ethylenenamides 5 is achieved via sodium cyanoborohydride reduction and acylation of the deoxybenzoin imines 2 , respectively. A new methodology for the synthesis of 3-arylisoquinolinium salts by the Bischler-Napieralski reaction of 1,2-diarylethylenenamides and their transformation into 12-methyl substituted benzo[c]phenanthridines has been developed.

The crystal structure of 2-acetamido-5-benzyloxy-carbonyl-3,4,5,6,7,8-hexahydro-4-oxo-6-(D-arabinotetrahydroxybutyl)pteridine tetraacetate, (5), shows that reduction of 2-acetamido-3,4-dihydro-4-oxo-6-(D-arabino-tetrahydroxybutyl)pteridine tetraacetate, (4), with sodium cyanoborohydride in the presence of benzyl chloroformate achieves saturation of the pyrazine ring with regioselective protection at nitrogen N(5)

The reductive amination of 4-phenyl-4-oxobutanal and 5-phenyl-5-oxopentanal with (S)-valine methyl ester and sodium cyanoborohydride afforded the N-substituted (S)-2-phenylpyrrolidine (88% d.e.) and (S)-2-phenylpiperidine (96% d.e.), from which the levorotatory NH cyclic amines were obtained. On the other hand, the analogous reductive amination of simple ketones, 2,5 hexanedione, and 2,6-heptanedione was poorly selective.

The fisetinidol-(4,8) and (4,6)-catechin profisetinidin biflavanoids 1,4 and 5 respectively, are subject to facile cleavage of the interflavanyl linkage with sodium cyanoborohydride in trifluoroacetic acid at 0 °C.

Starting from 7-alkoxy-4-aminocoumarins 5,6,8,12, and 13 as key intermediates, this paper describes two different methods for the preparation of azacannabinoidal 5H[1]benzopyrano[4,3-b]pyridin-5-ones 24–27, 38, and 39 containing typical structural requirements for ZNS activity. First, Michael addition of 6 and 8 to the double bonds of alkyl vinyl ketones 14 and 15 resulted in a mixture of tetrahydropyridines 24–27 and fused pyridines 20–23 the latter of which were reduced by sodium cyanoborohydride to give the target compounds 24–27. The second, pyridine ring closure was accomplished by a combination of Vilsmeier acetylation and formylation resulting in fused 4-chloropyridines 31–33 followed by reduction.

A convenient, mild and simple procedure, employing sodium cyanoborohydride in the presence of either catalytic or stoichiometric amount of boron trifluoride etherate in dry THF, for the reductive cleavage of the acetals and ketals is described.