The Chemistry Of The Euphorbiaceae. XXI. Compounds From Beyeria Brevifolia: (15S)-15,16-Dihydroxy-3,4-seco-enantio-pimara-4(18),7-dien-3-oic Acid
.The isolation of the title acid (I) together with a new flavone and known diterpenes of the beyerane and kaurane series is described. The structure (I) assigned to the new acid rests mainly on its conversion into 3,4-secobeyerane, which was partly synthesized. The configuration of C 15 was assigned on the basis of a method due to Horeau. The structure (XXX) of the new flavone was determined by degradation of the triethyl ether.