Migliaccio G P, Shieh T L, Byrn S R, Hathaway B A, Nichols D E
J Med Chem. 1981 Feb;24(2):206-9. doi: 10.1021/jm00134a016.
The 360-MHz 1H NMR spectra of bufotenin and psilocin were obtained, both as the free bases in CDCl3 and as protonated salts in D2O. Coupling constants for the side-chain methylenes were derived using the LAOCN3 program. These time-averaged coupling constants indicate that the trans and gauche rotamers of both compounds have about equal energy in D2O. There is a slight excess of the trans rotamer of bufotenin in CDCl3. For psilocin, in contrast, the gauche form is highly favored in CDCl3. The magnitude of this stabilization was estimated at about 1 kcal/mol using rotamer populations and free energy of transfer from published partitioning studies. It is suggested that this could result from a very weak hydrogen bond. On the other hand, the difference in partitioning between bufotenin and psilocin, which seems to be a major determinant of biological activity, is largely due to a difference in the basicity of the two compounds. The pKa values for the amino group of psilocin and bufotenin were determined to be 8.47 and 9.67, respectively.
获得了蟾蜍色胺和裸盖菇素的360兆赫1H核磁共振谱，二者均分别以CDCl3中的游离碱形式以及D2O中的质子化盐形式存在。使用LAOCN3程序得出侧链亚甲基的耦合常数。这些时间平均耦合常数表明，两种化合物的反式和顺式旋转异构体在D2O中的能量大致相等。在CDCl3中，蟾蜍色胺的反式旋转异构体略占优势。相比之下，对于裸盖菇素，顺式构象在CDCl3中极为有利。利用旋转异构体数量和已发表分配研究中的转移自由能，估计这种稳定作用的强度约为1千卡/摩尔。有人认为，这可能是由于一个非常弱的氢键所致。另一方面，蟾蜍色胺和裸盖菇素之间分配的差异似乎是生物活性的主要决定因素，这在很大程度上是由于两种化合物碱性的差异。已确定裸盖菇素和蟾蜍色胺氨基的pKa值分别为8.47和9.67。
