Thiopyran Route to Polypropionates: Aldol Diastereoselectivity of Linear and Two-Directional Iterative Homologations
作者:Dale E. Ward、Cheng Guo、Pradip K. Sasmal、Chuk C. Man、Marcelo Sales
DOI:10.1021/ol005790w
日期:2000.5.1
Aldol reaction of tetrahydro-4H-thiopyran-4-one with racemic 1,4-dioxa-8-thiaspiro[4.5]decane-6-carboxaldehyde is easily controlled to give the 2,3-anti-3,4-syn or the 2,3-syn-3,4-syn adduct. Aldol homologations of these beta-hydroxy ketones with the same aldehyde occur with considerable mutual kinetic enantioselection (MKE) and, in each case, selectively give one of the eight possible diastereomers. Similar reactions of related beta-methoxy ketones are also very diastereoselective but proceed without significant MKE, resulting in two diastereomers. The adducts can be used for polypropionate synthesis.