Asymmetric synthesis of hexapropionate synthons by sequential enantiotopic group selective enolization of meso diketones.
Meso 1,9-diketones (six to seven stereocenters) are readily obtained by stepwise or simultaneous two-directional aldol reactions of tetrahydro-4H-thiopyran-4-one with a thiopyran-derived aldehyde or dialdehyde. Enantioselective enolizations of these diketones with the lithium amide from (R,R)-bis(1-phenylethyl)amine occur with simultaneous kinetic resolution to give the mono-TMS enol ethers in >90% yields (BORSM) and >95% ee. The products are applicable to polypropionate synthesis. [reaction: see text]
Ward
Dale E
DE
Department of Chemistry, University of Saskatchewan, Saskatoon, SK S7N 5C9, Canada. dale.ward@usask.ca
Gillis
H Martin
HM
Akinnusi
Olukayode T
OT
Rasheed
M Abdul
MA
Saravanan
K
K
Sasmal
Pradip K
PK