52 トベラの新規C_<69>カロテノイドPittosporumxanthin A1およびA2の構造研究(口頭発表の部)

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In the course of the carotenoids research, we isolated two novel C_<69> carotenoids, named pittosporumxanthins A(1) and A2(2), from the seeds of Pittosporum tobira. The molecular formulae (C_<69>H_<104>O_6) of 1 and of 2 were determined by HRFAB-MS. The ^<13>C NMR spectra of 1 and 2 confirmed the presence of 69 carbons and the ^<13>C-^1H COSY spectra of 1 and 2 established all one-bond ^<13>C-^1H connectivities. The chemical shifts of all carbons of 1 were nearly identical to those of 2, except C11" and C27". DQF-COSY and HMBC experiments generated 11', 12'-dihydro-violaxanthin partial structure for both 1 and 2. The chemical shifts of unassigned carbons in 1 and 2 were similar to those of α-tocopherol expect that of C28". The connection of C12' to C28" in 1 and 2 was determined by HMBC and low power selective ^<13>C-{^1H}-NMR experiments. The relative stereochemistries in 1 and 2 were established by ROESY experiments (Fig. 4). The trans-configuration between H11' and H12' in 1 and 2 was deter-mined by the spin-coupling constant (9.3Hz) and the NOE data (Fig. 4 c,d). The absolute configurations of 3(S), 5(R), 6(S), 3'(S), 5'(R) and 6'(S) in both 1 and 2 were determined on the basis of the modified Mosher's method. Taking the absolute configurations of naturally occurring α-tocopherol [2"(R), 14'(R), 20"(R)], the relative stereochemistry of tetrahydrobenzodipyran ring (Fig. 4 c,d) and the chemical shift differences at C11" and C27" between 1 and 2 into consideration, 11'(R), 12'(S) and 11'(S), 12'(R) configurations were deduced for 1 and 2, respectively (Fig. 1).
天然有機化合物討論会の論文
1993-09-10

52 トベラの新規C_<69>カロテノイドPittosporumxanthin A1およびA2の構造研究(口頭発表の部)

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