Dibromocarbene was added to the double bond of 2 with formation of dib
romocyclopropyl cyclosporin 3 as a single isomer. Reduction of 3 gave
4. Hydrolysis with fluoride led to the unprotected cyclosporin 5. Remo
val of the silyl protecting group from 3 gave 6, which could also be o
btained directly from 1. The dibromocyclopropyl compound 6 was transfo
rmed to the allene 7 (mixture of diastereoisomers). The aldehyde 8 was
converted to 9 and rearranged to 10 (single isomer). Oxidation of 1 w
ith Jones reagent gave the ketone 11 (single isomer).