Tosylate 1, which features the vitamin D triene unit, was stereoselectively
synthesized from commercially available starting materials. This key inter
mediate undergoes a very efficient one-pot, two-step reaction with tetrabut
yl ammonium fluoride to afford vitamin D analogue 2, which bears a cyclic s
ide chain. Reaction of 1 with lithium aluminium hydride and removal of the
silyl protecting groups affords the 22-methylated vitamin D analogue 3. (C)
2001 Elsevier Science Ltd. All rights reserved.