Stereocontrol in organic synthesis using silicon-containing compounds.: Syntheses of (±)-2-deoxyribonolactone and (±)-arabonolactone

Samarium iodide reacts with-methyl (Z)-3-dimethyl(4-methylphenyl)silylprop-2-enoate 5b to give dimethyl (3RS,4SR)-3,4-bis[dimethyl(4-methylphenyl)silyl]hexane-1,6-dioate 8b with high-stereoselectivity This meso diester can be converted into (3RS,4SR)-3,4-bis[dimethyl(4-methylphenyl)silyl]-pentan-5-olide 16 by Dieckmann cyclisation, demethoxycarbonylation and Baeyer-Villiger reaction. Silyl-to-hydroxy conversion and relactonisation gave (+/-)-deoxyribonolactone, 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 thwarted by an unprecedented retention of configuration at the migration origin in the cationic rearrangement of (3RS,4SR)-3,4-bis[dimethyl(4-methylphenyl)silyl]-5-hydroxypentanoic acid 28 to (3RS,4SR)-3,5-bis[dimethyl(4-methylphenyl)silyl]pentan-1,4-olide 30.