Hybridaphniphyllines A and B, Daphniphyllum alkaloid and iridoid hybrids suggestive of Diels-Alder cycloaddition in Daphniphyllum longeracemosum

Abstract

Two Daphniphyllum alkaloid and iridoid hybrids with the hitherto unknown decacyclic fused skeletons, hybridaphniphyllines A and B, along with one diamino Daphniphyllum alkaloid, daphnicyclidin I, were isolated from dried stems and leaves of Daphniphyllum longeracemosum. Their structures were elucidated on the basis of extensive spectroscopic analysis, and the absolute configuration of daphnicyclidin I was deduced by the CD exciton chirality method. A biogenetic pathway for 1 and 2 involving natural Diels-Alder cycloaddition is proposed.

Keywords: Alkaloid and iridoid hybrid; C-22 nor-Daphniphyllum alkaloid; Daphniphyllaceae; Daphniphyllum longeracemosum; Diels–Alder cycloaddition; Hybridaphniphylline.