SYNTHESIS OF THE ENANTIOMERIC FUROBENZOFURANS, LATE PRECURSORS FOR THE SYNTHESIS OF (-AFLATOXINS AND (-)-AFLATOXINS B-1, B-2, G(1), AND G(2)())

Enantiomeric tetrahydrofuro[2,3-b]benzofurans, representing the ABC tr icyclic portion of aflatoxins B-1, B-2, G(1), and G(2), were generated from the oxaza-Cope rearrangement of a suitably functionalized O-aryl oxime. The O-aryloxime was, in turn, made from the condensation of an enantiomerically pure aldehyde derived from glutamic acid and a substi tuted phenoxyamine. High regioselectivity with respect to the A-ring s ubstituents of the ABC tricycle was achieved through the use of electr ochemistry. The regioselective electrochemical cleavage of arbonyl)-2, 3,3a,8a-tetrahydrofuro[2,3-b]benzofuran (22) resulted in a 97/3 mixtur e of regioisomeric phenols. The regiochemical assignments of the resul ting phenols were determined by 2D NOESY NMR. The enantiomeric ratio o f the final product was determined to be 96/4 by NMR analysis of diast ereomers resulting from the coupling of 31a to (+)- and (+/-)-phenethy lamine.