108(P59) 炭素-水素間の遠隔スピン結合定数を用いた天然物鎖状部分の立体配置解析法(ポスター発表の部)

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A new NMR methodology was developed for configurational assignments in acyclic structures of natural products. Unlike a conventional method based on NOE data, this methodology is applicable to stereochemical analysis even in the case multiple conformers are present since it is based on the dihedral angle dependency of long-range carbon-proton coupling constants (^<2,3>J_<C,H>)(Fig. 1). In this methodology, the combination of the coupling constants which are categorized to Large, Medium, or Small allows one to determine the relative stereochemistry among adjacent asymmetric centers or asymmetric centers separated by a methylene (Figs. 2, 3, and 4). The combined use of hetero half-filtered TOCSY (HETLOC) and phase-sensitive HMBC (PS-HMBC) experiment was shown to be effective for measuring ^<2'3>J_<C,H> values of complicated natural products (Figs. 6 and 7). Amphidinol 3 (AM3, 1), which was isolated from the dinoflagellate Amphidinium klebsii, was subjected to this methodology. To facilitate the measurements of ^<2'3>J_<C,H> of AM3, a ^<13>C-enriched sample was prepared by culturing the dinoflagellates in a medium containing 0.01% NaH^<13>CO_3. The cells obtained from 200L of the medium yielded 8mg of AM3, which was enriched with ^<13>C at ca. 25%. With this sample, 2D INEPT-INADEQUATE, which directly provides the information on C-C connectivity, was measured to confirm the proposed planar structure of AM3 and to assign the ^<13>C chemical signals unambiguously. Then HETLOC, PS-HMBC, and their variants were measured, and the coupling constants thus obtained, partly coupled with NOE data, led to the stereochemical assignments for the C20-C27 and C32-C51 portions of AM3 as shown in Fig. 5.
1997-07-20

108(P59) 炭素-水素間の遠隔スピン結合定数を用いた天然物鎖状部分の立体配置解析法(ポスター発表の部)

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