Gholam Hosein Hakimelahi

Nitrate ion as catalyst for selective silylations of nucleosides

Abstract Nitrate ion has been found to have a remarkable effect on the selectivity of silylation of ribonucleosides using the t -butyldimethylsilyl group.

High yield selective 3′-silylation of ribonucleosides

Abstract Procedures have been developed which permit the highly selective silylation of the 3′-hydroxyl of ribonucleosides to produce 3′,5′-diprotected derivatives in high yields.

Two Simple Methods for the Synthesis of Trialkyl α-Aminophosphono-Acetates (3). Trifluoromethanesulfonyl Azide as an Azide-Transfer Agent

Abstract In connection with a cephalosporin synthesis,1 Ratcliffe and Christensen reported the preparation of alkyl α-aminodiethylphos-phonoacetate2 3. We experienced considerable difficulty in repeating the procedure reported, and wish to describe alternate simple, high-yield preparations of 3.

A simple synthesis of 2,2-disubstituted tetrahydrothiophenes

Abstract Treatment of diethyl 2-(3-mesyloxypropyl) malonate with KSCOCH 3 /DMF at room temperature gave 2,2-dicarbethoxytetrahydrothiophene. The reaction can be used to prepare isopenams in good yield.

N-levulination of nucleosides

Abstract Procedures have been developed for the synthesis of the N-levulinyl derivatives of cytidine, adenosine and guanosine.

Silylated derivatives of arabinonucleosides

Abstract Procedure have been developed which allow for the selective derivatization of arabinonucleosides at the 5′− or 2′− and 5′− or 3′− and 5′− positions.

Conversion of ribonucleosides to protected 3′-deoxynucleosides

Abstract A procedure is presented for the conversion of ribonucleosides to 3′-deoxyribonucleosides and their protected derivatives.

Addition of elemental sulfur to carbanions and its application for synthesis of isopenams and isocephams

Abstract A new synthesis of isopenams and isocephams which involves sulfur addition to carbanions followed by internal alkylation is described.

Fluoride-Induced Cyclisation of Silyl Ethers with Mesylates and Chlorides. A High Yield Synthesis of 0-2-Isocephems

Abstract Doyle1 recently reported that conversion of benzyl ether 1a to benzo-O-2-isocephem 2a by sequential hydrogenolysis and base-induced cyclisation proceeded in 37% overall yield. We attempted a similar conversion 1b → 2b, which failed.