Oxindole alkaloids, isolated from the bark of Uncaria tomentosa [Willd. ex Schult.] Rubiaceae, are considered to be responsible for the biological activity of this herb. Five pentacyclic and two tetracyclic alkaloids were studied by solid-state NMR and theoretical GIAO DFT methods. The (13)C and (15)N CPMAS NMR spectra were recorded for mitraphylline, isomitraphylline, pteropodine (uncarine C), isopteropodine (uncarine E), speciophylline (uncarine D), rhynchophylline and isorhynchophylline. Theoretical GIAO DFT calculations of shielding constants provide arguments for identification of asymmetric centers and proper assignment of NMR spectra. These alkaloids are 7R/7S and 20R/20S stereoisomeric pairs. Based on the (13)C CP MAS chemical shifts the 7S alkaloids (delta C3 70-71ppm) can be easily and conveniently distinguished from 7R (deltaC3 74.5-74.9ppm), also 20R (deltaC20 41.3-41.7ppm) from the 20S (deltaC20 36.3-38.3ppm). The epiallo-type isomer (3R, 20S) of speciophylline is characterized by a larger (15)N MAS chemical shift of N4 (64.6ppm) than the allo-type (3S, 20S) of isopteropodine (deltaN4 53.3ppm). (15)N MAS chemical shifts of N1-H in pentacyclic alkaloids are within 131.9-140.4ppm.

中文翻译：

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（13）C，（15）N CPMAS NMR和GIAO DFT计算猫爪（Uncaria tomentosa）的立体异构体羟吲哚生物碱。

从毛indUncaria tomentosa的树皮中分离出来的羟吲哚生物碱[Willd。茜草科，被认为是这种草药的生物活性的原因。通过固态NMR和理论GIAO DFT方法研究了五个五环和两个四环生物碱。记录了（13）C和（15）N CPMAS NMR谱图，显示了米茶碱，异吗啉茶碱，翼蛇毒碱（恩卡因C），异戊足碱（恩卡因E），茶碱茶碱（恩卡因D），支气管茶碱和异吗啉茶碱。屏蔽常数的GIAO DFT理论计算为确定不对称中心和正确分配NMR光谱提供了依据。这些生物碱是7R / 7S和20R / 20S立体异构对。基于（13）C CP MAS的化学位移，可以轻松，方便地将7S生物碱（δC3 70-71ppm）与7R（δC374.5-74）区分开。9ppm），以及20S（deltaC20 36.3-38.3ppm）中的20R（deltaC20 41.3-41.7ppm）。茶碱的上型异构体（3R，20S）的特征在于，N4（64.6ppm）的N15（15）N MAS化学位移大于异戊二烯的异型（3S，20S）（δN453.3ppm）。（15）五环生物碱中N1-H的N MAS化学位移在131.9-140.4ppm之内。