Total Synthesis of the Putative Structure of Didemniserinolipids A and C

The total syntheses of the putative structure of serinolipid didemniserinolipids A and C have been achieved in 12 or 13 longest linear steps by divergent strategies starting from chiral pool methyl d-mannopyranoside, respectively. The key transformations include a sequential reaction of Bernet-Vasella-type reductive elimination and Horner-Wadsworth-Emmons in a one-pot process and a cascade reaction of desilylation/deacetalization/selective intramolecular spiroketalization involving the generation of the critical 6,8-dioxabicyclo[3.2.1]octane scaffold. Discrepancies in the spectroscopic data of the synthetic samples and natural products revealed that the original assignments of didemniserinolipids A and C were misassigned and warrant revision.