METHYLATION AND HYDROXYMETHYLATION INVOLVING FREE RADICALS. AN APPLICATION TO STEREOSELECTIVE CONSTRUCTION OF 20(S) STEROL SIDE-CHAIN

Article abstract of DOI:10.1016/S0040-4039(00)80404-9

Reductive radical cyclization of bromomethyl-silyl-ethers 1b and 2b was found to proceed in 5-exo-mode.Epimeric cyclic siloxanes 3 were transformed stereoselectively into 20(S) 25-hydroxycholesterol.Unsaturated (E) ester 4 was converted to its (Z) isomer 7 via saturation and selective dehydrogenation.