Tarek S. Mansour

Expeditious preparation of (−)-2′-deoxy-3′-thiacytidine (3TC)

Abstract The title compound has been prepared in enantiomerically pure form in four steps from (+)-thiolactic acid.

Oxidative degradation of L-ascorbic acid acetals to 2′,3′-dideoxy-3′-oxaribofuranosides. Synthesis of enantiomerically pure 2′,3′-dideoxy-3′-oxacytidine stereoisomers as potential antiviral agents

Abstract Enantiomerically pure 2′,3′-dideoxy-3′-oxacytidine nucleoside analogues were synthesized from L-ascorbic acid in eight steps and good overall yield.

The effect of additives on organolithiums

Abstract The effect of additives on the “apparent” acidities of weak carbon acids as measured versus lithiated amides is found to be small ( 2 pK units). TMEDA is found to be the most effective in accelerating the rates of deprotonation of triphenylmethane.

STRUCTURE-ACTIVITY RELATIONSHIPS AMONG A NEW CLASS OF ANTIVIRAL HETEROSUBSTITUTED 2',3'-DIDEOXYNUCLEOSIDE ANALOGUES

Abstract 3′-Oxa-4′-thiocytidine nucleoside analogues 14–17 were prepared from oxathiolanes 10 and 11, and evaluated for activity against HIV-1 and HBV in vitro. The nucleoside analogues were found to possess potent activities against HIV-1 in a panel of cell lines. Compound 16 is moderately active against HBV in 2.2.15 cells.

Synthesis of optically active 2',3'-dideoxy-3'-oxa-4'-thio-ribonucleoside analogues by transposition of a leaving group on chiral oxathiolanes via a reductive-oxidative process

Abstract The synthesis of chiral nucleoside analogues with a unique structural feature is reported. The strategy is based on a reductive-oxidative process to complete the transposition of the leaving group in chiral oxathiolanes with known configuration.

Antiviral optically pure dioxolane purine nucleosides analogues

Abstract Selective deamination of (±) cis 2,6-diaminopurine dioxolane nucleoside produces the (−) guanine analogue having the 2R,4R absolute stereochemistry. The (±) cis-adenine analogue generates the 2R,4R hypoxanthinyl derivative. Asymmetric synthesis of purine dioxolanes have been developed. The (−) adenine and (−) guanine compounds 6 and 7 emerged as potent inhibitors of the HIV-1 replication in vitro .

Divergent asymmetric syntheses of dioxolane nucleoside analogues

Abstract Oxidative degradation of benzyloxymethylacetals derived from D-mannitol or L-ascorbic acid provides dioxolane intermediate 6 and 7 useful in the synthesis of all the stereoisomers of dioxolane nucleoside analogues.

Unexpected effects of Lewis acids in the synthesis of optically pure 2′-deoxy-3′-oxacytidine nucleoside analogues

Abstract TiCl 4 and SnCl 4 promote the formation of dioxolane nucleosides with racemization in the coupling of enantiomerically pure 2′-deoxy-3′oxaribosides with silylated N -acetylcytosine. The use of TMSOTf, TMSI or TiCl 2 (Oi-Pr) 2 furnishes enantiomerically pure cytosine dioxolane nucleosides in low diastereoselectivity.

Carboxyl-modified amino acids and peptides. I: An efficient method for the synthesis of monofunctionalized enamines and monofunctionalized methyl ketone derivatives from thioamides via episulfides and thioiminium salts

Abstract Thioamides 4 were transformed by two convenient routes to various functionalized enamines 7 containing different electron-withdrawing groups E which on subsequent hydrolysis gave the corresponding methyl ketone derivatives 8 . Application of this methodology to obtain modified dipeptides at the carboxyl end, the determination of stereochemistry and the degree of racemization are discussed.

Diastereocontrol in glycosylation reactions: Synthesis of β-D and β-L dideoxycytidine analogues

Abstract Expeditious and diastereoselective total syntheses of the antiviral agents, β-L-ddC, β-L-5FddC and β-D-5FddC have been achieved in four steps from commercially available R-(-)-5-oxo-2-tetrahydrofurancarboxylic and its 2S isomer respectively.