Absolute configuration of flavanone–benzofuranone-type biflavonoids and 2-benzyl-2-hydroxybenzofuranones

Abstract

The O-1–C-2 and C-3–C-4 bonds in the flavanone–benzofuranone-type biflavonoids 1 and 3 are subject to cleavage with sodium cyanoboranuide in trifluoroacetic acid at 0 °C. Conformational information available from computational data in conjunction with ¹H NMR and CD spectroscopic observations of the biflavonoids and their degradation products have permitted assignment of absolute configuration to three biflavonoids and the 2-benzyl-2-hydroxy-1-benzofuran-3(2H)-one group of natural products.