Oligomeric isoflavonoids. Part 3. Daljanelins A–D, the first pterocarpan- and isoflavanoid-neoflavonoid analogues

Abstract

The structures of daljanelins A–C 1, 3 and 5, the first pterocarpan-neoflavonoid oligomers, and of daljanelin D 6 a related isoflavonoid-neoflavonoid analogue from Dalbergia nitidula were established by spectroscopic methods. The structure and stereochemistry of daljanelin C 5 were unambiguously confirmed by synthesis via introduction of an electrophilic C-1 fragment to a pterocarpan nucleus followed by anionic coupling of a C₆·C₂ precursor and the late introduction of the final C₆ fragment by a Grignard reaction.