197250-10-5Relevant articles and documents
Total synthesis of FK-506. Part 2: Completion of the synthesis
Ireland, Robert E.,Liu, Longbin,Roper, Thomas D.,Gleason, James L.
, p. 13257 - 13284 (1997)
The C15-C16 bond of FK-506 was formed via sulfone anion coupling followed by chelation controlled reduction of the C15 ketone. Efficient methylation of the C15-OH was accomplished by a combination of Me3OBF4-4A molecular sieves in the presence of Proton Sponge. A procedure was developed to avoid epimerization at the C2 position of the pipecolinate section during alkaline hydrolysis. A reductive fragmentation of the C21-C24 [6,6]-spiroketal iodide using active Zn/Aggraphite delivered the α'-allyl aldol section. The C9-C10 [5,6]-spiroketal acetonide was de-blocked via a novel β-elimination, using a combination of LiHMDS-Mg(HMDS)2 in HMPA-DME (I:]), to afford an enediol acetal, which was oxidized with dimethyl dioxirane to generate the C8-C10 a, P diketoanlide acetal function. Final desilylations completed the total synthesis of FK-506.