Novel alkaloids, paxdaphnines A and B with unprecedented skeletons from the seeds of Daphniphyllum paxianum

Two novel Daphniphyllum alkaloids with unprecedented skeletons, namely paxdaphnines A (1) and B (2), have been isolated from the seeds of Daphniphyllum paxianum. Paxdaphnine A (1) is a 19-nor-Daphniphyllum alkaloid with highly caged skeleton, and paxdaphnine B (2) is the first 1, 19-bisnor-Daphniphyllum alkaloid. The relative structures of 1 and 2 were elucidated by spectral methods, and their unique biosynthetic pathway postulated. The absolute structure of 1 was determined by X-ray diffraction of the iodide derivative (1a) of 1, and the absolute stereochemistry of 2 was proposed by correlation with the biosynthetic pathway for 1. (c) 2006 Elsevier Ltd. All rights reserved.