20 イチイ葉の微量成分の構造

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Ten minor constituents (2-11) have been isolated from Taxus Cuspidata Sieb. et ZUCC. in addition to the major constituent taxinine (Table 1). The strucures of 2 (O-cinnamoyltaxicin-I triacetate), 3 (taxinine A or TA), 4 (TH), 5 (TB), 6 (TE) and 7 (TJ) have already been clarified and are indicated in Fig. 1. I Structures of TK (8) and TL (9) and the photochemistry of taxinine. TL corresponds to the acetate of TK. Extensive NMR measurements of TK and TL employing decoupling and solvent shifts clarified the presence of the groupings summarized in Fig. 2; when the groups are fitted into the taxane skeleton it is noticed that C-3 and C-11 both have one unsatisfied valency suggesting that they should be linked. That this indeed is the case was established by the fact that irradiation of TA afforded TK in excellent yield (Fig. 3). Taxinine itself afforded phototaxinine in high yield (Fig. 4), the ease of ring closure obviously being due to the proximity of 3-H to the C_<11>-C_<12> double bond. II Nuclear Overhauser Effect (NOE) It was shown previously that the NOE can be a most powerful method in structural studies of rigid cage molecules; the NOE has also proven to be extremely useful in the taxinine series which have a more mobile ring structure. Protons connected by arrows in Fig. 5 are those exhibiting NOE' s. III Structures of TC (10) and TD (11) Spectroscopic data indicated the presence of the groups summarized in Table 2 and Fig. 6. Comparison of NMR data with the other taxinines and measurements of NOE's lead to two alternative structures 12a and 12b for TC and TD.
天然有機化合物討論会の論文
1967-09-25

20 イチイ葉の微量成分の構造

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