68 麻黄根の血圧下降成分Ephedradine類の構造

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From the crude drug "mao-kon", the underground part of Ephedra plants, a group of novel macrocylcic alkaloids, ephedradine A(I), B(VIII) and C(XII) have been isolated together with a new natural betaine maokonine. Administration of the dihydrobromide of ephedradines (III, IX, and XII) to urethane anesthetized rats (ca. 2 mg/kg, i.v.) caused a marked blood pressure fall. Ephedradine A(I), mp 166°, C_<28>H_<36>N_4O_4, afforded a crystalline dihydrobromide (III), mp 233-235°, [α]_D-102.0°. Detailed spectroscopic analysis as well as degradation experiments have informed the presence of two secondary amino groups, a para substituted phenoxyl group, a 2,3-trans-2,3,5-trisubstituted dihydrobenzofurane moiety in which the 2-position being benzylic, and a diacylated spermine moiety in I. From these informations together with the biogenetic considerations have envisaged a few possible structures, and the final conclusion has been drawn by the single crystal X-ray analysis of III. The absolute configuration has been established by ORD and CD measurements, as well as the X-ray method. Ephedradine B(VIII), amorphous solid, C_<29>H_<38>N_4O_5, afforded a crystalline dihydrobromide(IX), mp 219-221°, [α]_D-101.5°. Detailed comparative analysis of the spectroscopic data with those of I and its derivatives have indicated similarities of the structural features, in addition to the presence of a methoxyl group and two 1,2,4-trisubstituted phenoxy groups, leading to a conclusion that VIII to be a methoxyl derivative of I. The substituent has been located on C-12 from ^<13>C NMR calculations and NOE study. The same absolute configuration as I has been assigned also by the CD observation. Ephedradine C(XII), amorphous solid, C_<30>H_<40>N_4O_5, was also characterized as dihydrobromide (XIII), mp 224-226°, [α]_D-100.7°. The spectroscopic data are similar with those of VIII except the characteristic signals due to two methoxyl groups. Thus the structure was presumed to be the methyl ether of VIII, which was also supported by ^<13>C NMR calculations, and has been confirmed by chemical transformation of VIII to XIII. The absolute configuration has been concluded from the CD spectra.
天然有機化合物討論会の論文
1979-09-20

68 麻黄根の血圧下降成分Ephedradine類の構造

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