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A new reagent, 9-fluorenylmethoxy-carbonyl- N -hydroxy-3-azaspiro[5,5]undecane-2,4-dione ester (Fmoc-OASUD) for the preparation of Fmoc-amino acids is described. The Fmoc-OASUD reacts with amino acids at room temperature in the presence of a base and gives Fmoc-amino acids in high yields and purity. The Fmoc-amino acids prepared using Fmoc-OASUD are free from impurities due to Lossen rearrangement, which are generally present when Fmoc-OSu is used. This is mainly because of the higher stability of Fmoc-OASUD compared to Fmoc-OSu.

A simple and efficient method has been developed for the synthesis of 2-aminothiazoles from α-diazoketones using PEG-400 solvent system. This novel synthetic approach involves the reaction between thiourea and α-diazoketones in PEG-400 at 100 °C to yield the corresponding 2-aminothiazoles in good yields. The method is simple, rapid and generates thiazole derivatives in excellent yields without the use of any catalysts. This green protocol can be utilized for fast synthesis of various 2-aminothiazoles in good yields.

This Account summarizes the evolution of versatile ruthenium (II) complexes for annulations of alkynes via C_H/N_H, C_H/O_H, or C_H/N_O bond cleavages. To achieve selective C_H bond functionalizations, we needed to understand the detailed mechanism of the crucial C_H bond metalation with ruthenium (II) complexes and particularly the importance of carboxylate assistance in this process. As a consequence, our recent efforts have resulted in widely applicable methods for the versatile preparation of differently decorated arenes and heteroarenes, providing access to among others isoquinolones, 2-pyridones, isoquinolines, indoles, pyrroles, or r-pyrones. Most of these reactions used Cu (OAc)2 H2O, which not only acted as the oxidant but also served as the essential source of acetate for the carboxylate-assisted ruthenation manifold. Notably, the ruthenium (II)-catalyzed oxidative annulations also occurred under an ambient atmosphere of air with cocatalytic amounts of Cu(OAc)2 3 H2O. Moreover, substrates displaying N_O bonds served as “internal oxidants” for the syntheses of isoquinolones and isoquinolines. Detailed experimental mechanistic studies have provided strong support for a catalytic cycle that relies oninitial carboxylate-assisted C_H bond ruthenation, followed by coordinative insertion of the alkyne, reductive elimination, and reoxidation of the thus formed ruthenium(0) complex.

3-Azaspiro-[5,5]-undecane-2, 4-dione (2, Scheme 1 ) is an important intermediate for the preparation of gabapentin, 1 – 3 which is widely used in the treatment of epilepsy and other various cerebra...

The scope of nickel boride as a versatile reducing reagent is extended to the 3-oxidopyrylium-alkene [5 + 2] cycloadducts. In this report, we demonstrate that nickel boride is capable of one-pot 1,2- and 1,4-reduction of enones present in the cycloadducts in good yields. Subsequent elaboration of the cycloadducts towards synthesis of functionalized cycloheptenoid derivatives devoid of the oxa-bridge is also explored.

The synthesis of the anti-asthmatic compound CMI-977 is described. The tetrahydrofuran ring was effectively constructed by involving olefin metathesis while the stereoselective introduc- tion of the 1-N-hydroxyureidylbut-3-yn-4-yl side-chain was achieved by C-alkylation of the 2-benzenesulfonyl derivative. The role of leukotrienes in inflammatory and allergic re- sponses including arthritis, asthma, psoriasis, and throm- botic disease has been well recognized. The urge to develop antagonists or inhibitors of leukotriene biosyn- thesis to prevent inflammatory responses is an ongoing process. 1 Various 2,5-disubstituted tetrahydrofuran deriv- atives have been reported with lipoxygenase inhibitory activity. 2 However, (2S,5S)-5-(4-fluorophenoxylmethyl)- 2-(1-N-hydroxyureidylbut-3-yn-4-yl)tetrahydrofuran (CMI-977) (1) is by far the most potent compound report- ed in this series. 3 In this communication, we report a new approach to 2,5-disubstituted tetrahydrofuran (CMI -977) as well as to the corresponding six-membered 2,6-disub- stituted pyran analogue 2 based on (i) the olefin metathesis 4 and (ii) a stereoselective alkylation of 2-ben- zenesulfonyl derivatives. 5

Highly efficient, asymmetric total syntheses of the title phospholipids as well as short chain and cross-linkable aminoether analogs were achieved in five to seven steps from a readily available myo -inositol derivative.

A simple one-step synthesis was accomplished for the preparation of N-phosphoramidophosphonates by a direct reaction of phosphoramidate (1) with heterocyclic aldehydes (2a—j) and dialkyl phosphites at 60—70 °C in the presence of tetramethylguanidine. The tetramethylguanidine not only catalyses this reaction but also helps to form pure products in high yields in lesser time. They exhibited good insecticidal and antioxidant properties.

An effective synthesis is described for the preparation of all four mono trans isomers of arachidonic acid via deoxidation of epoxide precursors with lithium diphenylphosphide and quaternization with methyl iodide.

Cytochrome P450BM3 and its F87V mutant were exploited for a convenient, laboratory scale (1 mmol) preparation of 14( S ),15( R )-epoxyeicosatrienoic acid [14( S ),15( R )-EET] from arachidonic acid and (+)-leukotoxin B [(+)-12( S ),13( R )-vernolic acid] from linoleic acid, respectively. Their enantiomers were accessed via a four-step chemical inversion.

Mild, room temperature CrCl 2 reduction of 1,1,1-trichloroalkanes stereoselectively generates ( Z )-1-chloro-2-substituted-1-alkenes in excellent yields.

The vinyl arenes undergo smooth hydroamination with sulfonamides in the presence of 10 mol % of iodine to furnish tosyl and mesyl-protected secondary amines in excellent yields in short reaction times. The use of inexpensive and readily available molecular iodine makes this method quite simple, more convenient, and practical.

The direct thiocyanation of indoles and pyrrole with ammonium thiocyanate has been achieved using o-iodoxybenzoic acid (IBX) under mild and neutral conditions to produce indol-3-yl and pyrrol-2-yl thiocyanates, respectively, in excellent yields and with high selectivity. This method is effective even with N-substituted arylamines for the preparation of aryl thiocyanates.

Direct substitution of the hydroxy group in 2-propynyl alcohols with sulfonamides has been achieved using 5 mol % of phosphomolybdic acid supported on silica gel (PMA/SiO2) under mild reaction cond...

A simple and efficient stereoselective total synthesis of tarchonanthuslactone and formal synthesis of (-)-colletol is described using as the key steps Jacobsen's kinetic resolution and a Sharpless asymmetric epoxidation. The synthesis of tarchonanthus- lactone and the seco acid proceeded in 14% and 13% overall yield, respectively, starting from chiral (R)-propylene oxide.

We have achieved a short, efficient stereoselective synthesis of 7-membered oxepane derivatives with potential against asthma. Highlights of our synthetic strategy are regioselective oxidation of a hydroxyl group and efficient ring closure of an open chain aldehyde to a 2-benzenesulfonyl oxepane derivative with PhSO 2 H. Surprisingly the cis -isomer showed better activity than the trans -isomer.

A facile route to the synthesis of enantiomeric oxa-bridged bicycloadducts 9 and 18 has been developed employing an intramolecular [5+2] cycloaddition of 3-oxidopyrylium with unsaturated sugars.

Chemical examination of the marine sponge Iotrochota baculifera of the Indian Ocean furnished a sphingolipid (1), a new glycosphingolipid (iotroridoside-B, 2) and a four-component mixture of sphingolipids (3a-d) with two new components. Structure elucidation was carried out by spectral and chemical methods.