Oxidative Degradation of a Bis(γ-butyrolactone) into a Stereodefined 1,3,7,9-Tetraol. Enantioselective Synthesis of a 1,3,5,7,9-Pentaol Building Block for Polymethoxylated Marine Natural Products
22 March 2002 (online)
A stereoselective synthesis of the protected skipped all-syn pentaol 18 based on our γ-butyrolactone → 1,3-diol degradation is described. Lactone 7, readily accessible from L-glutamic acid, and the dibromoisobutene equivalent 6 were elaborated in three steps into bislactone 10 having four stereogenic centers. Oxidative degradation of both lactone moieties via a double Criegee rearrangement of a bis(peroxosulfonate) gave the diastereomerically pure tetraol 11. Ozonolytic cleavage of its C=C bond followed by chelation-controlled reduction with Zn(BH4)2 led to the fifth hydroxy group with ds ≥ 10:1.