126822-63-7Relevant articles and documents
Total synthesis of furanocembranolides. 1. Stereocontrolled preparation of key heterocyclic building blocks and assembly of a complete seco-pseudopterane framework
Paquette, Leo A.,Doherty, Annette M.,Rayner, Christopher M.
, p. 3910 - 3926 (2007/10/02)
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 substrates 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. Transformation of the (phenylthio)methyl substituent of 27 into the requisite isopentenyl side chain was next accomplished in five steps. Because alkylation α to the lactone carbonyl in 46 could be realized only in modest yield, this final segment of the intended macrocyclic ring was introduced earlier by more convergent means. Indeed, the coupling of 24 to 52 proved to be efficient and highly diastereoselective. Following an unsuccessful attempt to introduce the isopentenyl side chain after elaboration of the butenolide subunit, the chemical sequence was reversed. The dual selenenylation strategy for oxidation of both relevant pendant groups was notably effective for this purpose. The subsequent chemospecific attachment of the isobutenyl fragment onto bromide 62 was achieved by palladium(0)-catalyzed coupling to a vinylstannane in a process that promises considerable versatility. Further chemical manipulation gave rise to the seco-pseudopterane 71, thereby completing the intermediate stages of the total synthesis of the pseudopterane ring system.
