Approaching the C33-C38 fragments of amphotericin B and nystatin by a retro-[1,4]-Brook rearrangement and the stereoselective manipulation of the resulting allylsilane

Article abstract of DOI:10.1055/s-1998-1599

Sulfide S-4 (98.6% ee) furnished allylsilane S,S-anti-2 through a potassium naphthalenide induced, highly stereoselective retro-Brook rearrangement. Treatment with diethylborane followed by NaOOH/H₂O₂ delivered alcohol 9 as a single diastereomer. Cylization (→10), oxidation (→16), and methylation gave ketone 17. Reduction of 17 with Et₃SiH in CF₃CO₂H was accompanied by an unprecedented rearrangement of the neighboring oxasilolane ring to the C-silylated tetrahydropyran 20. It was oxidized to alcohol 21 which - if one inverted its OH group - would become a new C₃₃-C₃₈ building block for the polyol/polyene antibiotics amphotericin B and nystatin.