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.