Stereocontrolled facile synthesis and biological evaluation of (3'S) and (3'R)-3'-amino (and Azido)-3'-deoxy pyranonucleosides

Synthesis of a cyclic tetramer of 3-amino-3-deoxyallose with axially oriented amino groups

A linear tetramer of β-(1 → 6)-linked 3-azido-3-deoxy-d-allose containing glycosyl donor and glycosyl acceptor functions in the terminal monosaccharide units was prepared starting from 3-azido-3-deoxy-1,2:5,6-di-O-isopropylidene-α-d-allofuranose. Cyclization of the linear tetramer under glycosylation conditions afforded the corresponding cyclic tetrasaccharide in 77% yield; its deprotection and reduction of the azido groups resulted in the formation of the cyclic tetramer of 3-amino-3-deoxy-d-allose with axial amino groups, a potential scaffold for the synthesis of tetravalent functional clusters.

Synthesis of novel N-acyl-β-d-glucopyranosylamines and ureas as potential lead cytostatic agents

Novel classes of acetylated and fully deprotected N-acyl-β-d-glucopyranosylamines and ureas have been synthesized and biologically evaluated. Acylation of the per-O-acetylated β-d-glucopyranosylurea (5), easily prepared via its corresponding phosphinimine derivative, by zinc chloride catalyzed reaction of the corresponding acyl chlorides RCOCl (a-f) gave the protected N-acyl-β-d-glucopyranosylureas (6a-f), in acceptable-to-moderate yields. Subsequent deacetylation of analogues 6a-f under Zemplén conditions afforded the fully deprotected derivatives 7a,b,d,e,f, while the desired urea 7c was formed after treatment of 6c with dibutyltin oxide. All protected and unprotected compounds were examined for their cytotoxic activity in different L1210, CEM and HeLa tumor cell lines and were also evaluated against a broad panel of DΝΑ and RNA viruses. Derivative 7c exhibited cytostatic activity against the three evaluated tumor cell lines (IC₅₀ 9-24 μΜ) and might be the basis for the synthesis of structure-related derivatives with improved cytostatic potential. Only analogue 6f weakly but significantly inhibited the replication of parainfluenza-3 virus, Sindbis virus and Coxsackie virus B4 in cell cultures at concentrations of 45-58 μM.

Branched-chain sugar nucleosides: stereocontrolled synthesis and bioevaluation of novel 3'-C-trifluoromethyl and 3'-C-methyl pyranonucleosides

A new series of 3'-C-trifluoromethyl- and 3'-C-methyl-β-d-allopyranonucleosides of 5-fluorouracil and their deoxy derivatives has been designed and synthesized. Treatment of ketosugar 1 with trifluoromethyltrimethylsilane under catalytic fluoride activation and methyl magnesium bromide, gave 1,2:5,6-di-O-isopropylidene-3-C-trifluoromethyl (2a) and 3-C-methyl (2b)-α-D-allofuranose, respectively, in a virtually quantitative yield and with complete stereoselectivity. Hydrolysis followed by acetylation led to the 1,2,4,6-tetra-O-acetyl-3-C-trifluoromethyl (3a) and 3-C-methyl (3b)-β-D-allopyranose. Compounds 3a,b were then condensed with silylated 5-fluorouracil and deacetylated to afford the target nucleosides 5a,b. Deoxygenation of the peracylated allopyranoses 3a,b followed by condensation with silylated 5-fluorouracil and subsequent deacetylation yielded the target 3'-deoxy-3'-C-trifluoromethyl and 3'-deoxy-3'-C-methyl-β-d-glucopyranonucleosides 14a,b. The newly synthesized compounds were evaluated for their potential antiviral and cytostatic activities. The 3'-deoxy-3'-C-methyl- ribonucleoside 11b showed significant cytotoxic activity (∼7 μM) almost equally active against a variety of tumor cell lines.