New Alkaloids of the ent-Kaurene Type From Anopterus Species. II. The Structure of the Minor Alkaloids

Abstract

Anopterimine (2) is a new diterpenoid alkaloid, and on the basis of spectroscopic data it is considered to have the same carbon skeleton as anopterine. It is remarkable in having a C19-N azomethine system, while another minor base of A. macleayanus is anopterimine N-oxide (3). Two other new alkaloids, hydroxyanopterine and dihydroxyanopterine, both resemble anopterine, and spectroscopic data indicate that they have an additional hydroxy group at C1 or C3 on the A ring. Dihydroxy- anopterine has tiglic acid and the new acid, (E)-4-hydroxy-2-methylbut-2-enoic acid, as esterifying acids. A biosynthetic route to the Anopterus alkaloids is suggested.