14 アキタブキ・ふきのとうの一成分,Bakkenolide-Aの構造

抄録

Two new sesquiterpenes, Bakkenolide-A, C_<15>H_<22>O_2, m.p. 80-81°and Bakkenolide-B C_<22>H_<30>O_6, m.p. 101-102°, were isolated from the bud of Petasites japonious subsp. giganteus Kitam (Japanese name, AKITABUKI). Structure (5d), including the absolute configuration, was established for Bakkenolide-A (B-A) on the basis of the chemioal degradations (chart I) and their physical measurements (Fig 1 and 2). One of the main degradations was a oonversion of B-A to C_<11>-dioarboxylic acid (2), structure of which was deduced from NMDR technique. The combination of 2 with the new type of spiro laotone (5a) as a partial structure led to the final structure 5C for B-A. The absolute configuration was determined by the transformation of B-A to the known ketone (14). The comparisons of the physical properties of Bakkenolide-B (B-B) with B-A led to the structure 16 for B-B, which will be discussed near future.