Total synthesis of furanocembranolides. 1. Stereocontrolled preparation of key heterocyclic building blocks and assembly of a complete seco-pseudopterane framework

A retrosynthetic strategy for the total synthesis of pseudopterolide and allied pseudopteranes is presented. This scheme is dependent upon early elaboration of suitable 2,5-difunctionalized 3-furoate esters. To this end, the pair of useful substrate 21 and 24 was readily synthesized from 2,3-O-isopropylidene-D-glyceraldehyde and methyl 4(phenylthio)acetoacetate. The conversion of both of these intermediates into furanolactone 27 was next studied. The best method for gaining suitable control of stereochemistry involved condensation of 24 with methyl 3-formylpropionate under conditions of boron trifluoride catalysis