The thiopyran route to polypropionates: enantioselective synthesis of membrenone B from racemic fragments.
(6S,7S,8S,9R,10S)-(--)-Membrenone B was synthesized in nine steps (9.4% overall yield) beginning with two-directional aldol coupling of tetrahydro-4H-thiopyran-4-one with racemic 1,4-dioxa-8-thiaspiro[4.5]decane-6-carboxaldehyde. The first aldol reaction occurs with dynamic kinetic resolution to give a single adduct (>98% ee). The second aldol reaction is highly diastereoselective (three of eight possible adducts), and both major products are converted to membrenone B. The route also constitutes a formal synthesis of membrenone A.
Jheengut
Vishal
V
Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon SK S7N 5C9, Canada.
Ward
Dale E
DE
D011422:Propionates / Q000138:chemical synthesis*; D011714:Pyrans / Q000737:chemistry*; D011753:Pyrones / Q000138:chemical synthesis*; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry*