Reactivity of (1-methoxycarbonylpentadienyl)iron(1+) cations with hydride, methyl, and nitrogen nucleophiles

The reaction of tricarbonyl and (dicarbonyl)triphenylphosphine (1-methoxycarbonyl-pentadientyl)iron(1+) cations 7 and 8 with methyl lithium, NaBH3CN, or potassium phthalimide affords (pentenediyl)iron complexes 9a-c and 11a-b, while reaction with dimethylcuprate, gave (E,Z-diene)iron complexes 10 and 12. Oxidatively induced-reductive elimination of 9a-c gave vinylcyclopropanecarboxylates 17a-c. The optically active vinylcyclopropane (+)-17a, prepared from (1S)-7, undergoes olefin cross-metathesis with excess (+)-18 to yield (+)-19, a C9C16 synthon for the antifungal agent ambruticin. Alternatively reaction of 7 with methanesulfonamide or trimethylsilylazide gave (E,E-diene)iron complexes 14d and e. Huisgen [3 + 2] cyclization of the (azidodienyl)iron complex 14e with alkynes afforded triazoles 25a-e

Synthesis and biological evaluation of 3′-c-ethynyl and 3′-c-(1,4-disubstituted-1,2,3-triazolo) double-headed pyranonucleosides

A novel series of 3′-C-ethynyl and 3′-C-(1,4-disubstituted-1,2, 3-triazolo) double-headed pyranonucleosides has been designed and synthesized. Reaction of 3-keto glucoside 1 with ethynyl magnesium bromide gave the desired precursor 3-C-ethynyl-1,2:5,6-di-O-isopropylidene-α-D-allofuranose (2). Hydrolysis followed by acetylation led to the 1,2,4,6-tetra-O-acetyl-3-C- ethynyl-β-D-allopyranose (3). Compound 3 was condensed with silylated 5-fluorouracil, uracil, thymine, N4-benzoylcytosine and N 6-benzoyladenine, respectively and deacetylated to afford the target 1-(3′-C-ethynyl-β-D-allopyranosyl)nucleosides 5a-c,f,g. Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) reaction was utilized to couple the 3′-C-ethynyl pyranonucleoside derivatives with azidoethyl adenine, 5-fluorouracil and thymine, respectively to afford novel triazole double-headed nucleoside analogues 8a-h. 3′-C-Ethynyl pyranonucleosides and the new doubleheaded analogues were evaluated for their antiviral and cytostatic activities. Although none of the compounds showed pronounced cytostatic activity and were devoid of a significant antiviral potential, the double-headed nucleoside derivatives 8a, 8c and 8e showed a moderate cytostatic activity against human cervix carcinoma HeLa cells which may be the basis for the synthesis of analogous derivatives with improved cytostatic potential. © 2012 Bentham Science Publishers