STEREOCONTROL IN ORGANIC-SYNTHESIS USING SILICON-CONTAINING COMPOUNDS- SYNTHESES OF (+ -)-2-DEOXYRIBONOLACTONE AND (+/-)-ARABONOLACTONE/

Samarium iodide reacts with-methyl (Z)-3-dimethyl(4-methylphenyl)silyl prop-2-enoate 5b to give dimethyl is[dimethyl(4-methylphenyl)silyl]hex ane-1,6-dioate 8b with high-stereoselectivity This meso diester can be converted into -bis[dimethyl(4-methylphenyl)silyl]-pentan-5-olide 16 by Dieckmann cyclisation, demethoxycarbonylation and Baeyer-Villiger r eaction. Silyl-to-hydroxy conversion and relactonisation gave (+/-)-de oxyribonolactone, and anti-selective enolate hydroxylation followed by silyl-to-hydroxy conversion gave (+/-)-arabonolactone. An attempt to synthesise sugars with the relative configuration (3RS,4RS) was thwart ed by an unprecedented retention of configuration at the migration ori gin in the cationic rearrangement of [dimethyl(4-methylphenyl)silyl]-5 -hydroxypentanoic acid 28 to bis[dimethyl(4-methylphenyl)silyl]pentan- 1,4-olide 30.