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β-Enamino esters, thioesters and amides are formed from the corresponding β-keto compounds and amines in the presence of mild peptide coupling reagents.

Recent progress in the development and application of signal enhancement methods for NMR of quadrupolar nuclei in solids is presented. First, various pulse schemes for manipulating the populations of the satellite transitions in order to increase the signal of the central transition (CT) in stationary and rotating solids are evaluated (e.g., double-frequency sweeps, hyperbolic secant pulses). Second, the utility of the quadrupolar Carr-Purcell-Meiboom-Gill (QCPMG) and WURST-QCPMG pulse sequences for the rapid and efficient acquisition of particularly broad CT powder patterns is discussed. Third, less frequently used experiments involving polarization transfer from abundant nuclear spins (cross-polarization) or from unpaired electrons (dynamic nuclear polarization) are assessed in the context of recent examples. Advantages and disadvantages of particular enhancement schemes are highlighted and an outlook on possible future directions for the signal enhancement of quadrupolar nuclei in solids is offered.

Asymmetric hydrogenation routes to homologues of The Roche ester tend to be restricted to hydrogenations of itaconic acid derivatives, that is, substrates that contain a relatively unhindered, 1,1-disubstituted alkene. This is because in hydrogenations mediated by RhP2 complexes, the typical catalysts, it is difficult to obtain high conversions using the alternative substrate for the same product, the isomeric trisubstituted alkenes (D in the text). However, chemoselective modification of the identical functional groups in itaconic acid derivatives are difficult; hence, it would be favorable to use the trisubstituted alkene. Trisubstituted alkene substrates can be hydrogenated with high conversions using chiral analogs of Crabtree’s catalyst of the type IrN(carbene). This paper demonstrates that such reactions are scalable (tens of grams) and can be manipulated to give optically pure homo-Roche ester chirons. Organocatalytic fluorination, chlorination, and amination of the homo-Roche building blocks was p...

The method for the synthesis of 1,5-disubstituted triazolones involves the reaction of dilithiated Boc-hydrazines with substrates (I) or (IV).

The controlled conversion of hydrocarbons to functionalized products requires selective C–H bond cleavage. This perspective provides an overview of 1,2-CH-addition of hydrocarbons across d0 transition metal imido complexes and compares and contrasts these to examples of analogous reactions that involve later transition metal amide, hydroxide and alkoxide complexes with d6 and d8 metals.

BODIPY dyes tend to be highly fluorescent, but their emissions can be attenuated by adding substituents with appropriate oxidation potentials. Substituents like these have electrons to feed into photoexcited BODIPYs, quenching their fluorescence, thereby generating relatively long-lived triplet states. Singlet oxygen is formed when these triplet states interact with 3O2. In tissues, this causes cell damage in regions that are illuminated, and this is the basis of photodynamic therapy (PDT). The PDT agents that are currently approved for clinical use do not feature BODIPYs, but there are many reasons to believe that this situation will change. This review summarizes the attributes of BODIPY dyes for PDT, and in some related areas.

As methodology development matures, it can be difficult to discern the most effective ways of performing certain transformations from the rest. This review summarizes the most important contributions leading to asymmetric hydrogenations of simple unsaturated acid and ester substrates, with the objective of highlighting at least the best types of catalysts for each. Achievements in the area are described, and these reveal situations where further efforts should be worthwhile and ones where more research is only likely to give diminishing returns. In general, our conclusions are that the most useful types of catalysts for unsaturated acids and esters tend to be somewhat different, simple substrates have been studied extensively, and the field is poised to address more complex reactions. These could be ones involving alternative (particularly cyclic) structures, chemoselectivity issues, and more complex substrate stereochemistries.

A variety of functionalized acid-sensitive vinyl ethers is successfully hydrogenated in the presence of a chiral Ir—N-carbene—oxazoline complex (ICOC).

In the presence of IRC, allyl amines of type (I) and (IV) smoothly undergo asymmetric hydrogenation to afford title compounds like (II) and (III).

Many “new generation” peptidomimetics are designed to present amino acid side chains only; they do not have structural features that resemble peptide main chains. These types of molecules have frequently been presented in the literature as mimics of specific secondary structures. However, many “side-chain only” peptidomimetics do notrest in single conformational states, but exist in a limited number of freely interconverting forms. These different conformations may resemble different secondary structures, so referring to them as, for instance, turn- or helical-mimics understates the ways they could adapt to various binding situations. Sets of scaffolds that can be used to mimic aspects of nearly every secondary structure, i.e. universal peptidomimetics, can be constructed. These may assume a privileged place in library design, particularly in high throughput screening for pharmacological probes for which binding conformations, or even the target itself, is unknown at the time the library is designed (critical review, 101 references).

A novel γ-turn mimetic 2 has been prepared based on retro amide peptide design. Incorporation of this mimetic into linear peptide fibrinogen receptor antagonist 7 (GPIIb/IIIa receptor) affords the opportunity to test models of antagonist pharmacophore.

The title compounds have been prepared from 3-acylpropionic acids 2 and (−)-R-phenylglycinol in a three-step sequence in >98% enantiomeric excess. The R group in 2 ultimately becomes the 2-substituent in the chiral pyrrolidine

Tetrahydrofuran, 1,3-dioxolane, hexanal, and benzaldehyde react readily with β,β-difluoroacrylates under free radical conditions to furnish adducts in moderate to high yield.

Two methods are presented for kinetic resolutions of compounds containing ester and sulfoxide functionalities (sulfinylalkanoates). In the first a crude lipase preparation from Pseudomonas sp. (K10) mediates enantioselective hydrolysis of these esters in an aqueous environment. The second method uses the same lipase preparation to promote enantioselective transestesterifications with alcohols in hexane

An efficient procedure for the preparation of the title compounds in high enantiomeric purity has been realized starting from 3-acylpropionic acids. Stereoselective reduction of chiral bicyclic lactams 2a-h, prepared from the corresponding γ-keto acid and (R)-phenylglycinol, using alane or triethylsilane with titanium tetrachloride provided the N-substituted pyrrolidines and pyrrolidinones, respectively. Subsequent cleavage of the phenylglycinol returned the desired amines and lactams. The enantiomeric purity of these compounds was determined to be >98% by chiral stationary-phase HPLC

D-1,6-Diepicastanospermine has been prepared via reaction of an allylstannane with the arabinose derivative 1a. This reaction was almost 100 % stereoselective, but the corresponding allylations of aldehydes 1b–d gave mixtures of isomers. Variable stereodifferentiation in these reactions can be attributed to the influence of the distal (γ) chiral center.

Asymmetric synthesis of all four stereoisomers of 2,3-methanomethionine ((Z)- and (E)-cyclo-Met) are described. The source of chirality in these reactions is a trifluoromethysulfonate ester 1b which reacts with di-tert-butyl malonate via direct displacement of trifluoromethysulfonate followed by lactonization to give 1-(tert-butoxycarbonyl)-2-oxo-3-oxabicyclo[3.1.0]hexane (2). Conversion of compound 2 into (Z)-cyclo-Met can be achieved via ring opening of the lactone, Hoffmann rearrangement, mesylation, and displacement with thiomethoxide. A route to (E)-cyclo-Met was developed using a lipase to effect a critical ester hydrolysis

The reaction of the anion of ethyl isocyanoacetate with suitably substituted vinyl p- tolyl sulfones gives fair to good yields of pyrrole-2-carboxylates substituted in the 3-, 4- or 3- and 4-positions. From the reaction of 1-phenyl-1-tolylsulfonylethene with ethyl isocyanoacetate , two diastereoisomers of ethyl 4,6-diphenyl-4,6-bis(p- tolylsulfonyl )-3,4,5,6-tetrahydro-2H-azepine-2-carboxylate (4) were also isolated.

Two derivatives of thymidine, a 5′-protected 3-hydroxylamine and 5′-carboxy-3′-protected compound, were prepared and coupled to form an oxyamide-linked dinucleotide analogue; this dimer was incorporated into an oligodeoxynucleotide then shown to anneal to complementary DNA with nearly the same affinity as the natural sequence.

Bis(mesityl)niobium (1) promotes hydroborations of alkenes by catecholborane but via an indirect mechanism.

The deoxynojirimycin analogs (4) and (5) were prepared via addition of a metallated imidazole to an aldehyde; these compounds were screened for inhibition of glycosidase enzymes and anti-HIV activities

The syntheses of two monocyclic 1,3-dioxane tricarboxylic acid analogues of the natural product squalestatin 1 are described herein. Their activity against both mammalian (rat liver) and fungal (Candida albicans) squalene synthase is also reported.