Wagner-Meerwein Rearrangement of Duocarmycins.
作者:Satoru NAGAMURA、Yutaka KANDA、Akira ASAI、Eiji KOBAYASHI、Katsushige GOMI、Hiromitsu SAITO
DOI:10.1248/cpb.44.933
日期:——
We found that treatment of the 8-O-protected-3-hydroxy derivatives of duocarmycin B2 (DUMB2, 1c) with camphorsulfonic acid (CSA) in toluene interestingly gave A-ring pyrrole analogs of DUMB2 (1c) in good yields. Their structures were unambiguously elucidated on the basis of NMR and mass spectrometry, and the mechanism was considered to be a Wagner-Meerwein type rearrangement. On the other hand, treatment of the 9-O-protected-3-hydroxy derivatives of duocarmycin B1 (1b) with CSA afforded different rearrangement products. In the case of bulky groups at the 9-O position, such as a tert-butyldimethylsilyl group, normal A-ring pyrrole analogs were obtained. Under the same condition, however, the 9-O-N, N-dimethylcarbamoyl-3-hydroxy compound of 1b gave a spiro compound, which was derived from a 1, 2-shift of the methoxycarbonyl group and a bonding between the C-8 position and the C-2' position. Compounds having a protective group of medium size gave a mixture of the normal rearrangement and the spiro derivative.
我们发现,在甲苯中,使用樟脑磺酸(CSA)处理8-O保护的3-羟基衍生物DUMB2(1c)时,有意思的是以良好产率得到了DUMB2(1c)的A环吡咯类似物。它们的结构根据核磁共振(NMR)和质谱明确阐明,并且认为其机制是瓦格纳-迈尔外因重排。另一方面,使用CSA处理9-O保护的3-羟基衍生物DUMB1(1b)则得到了不同的重排产物。在9-O位置有较大的基团,如叔丁基二甲基硅基团的情况下,得到了正常的A环吡咯类似物。然而,在相同条件下,9-O-N,N-二甲基氨基甲酰基-3-羟基化合物1b生成了螺环化合物,这是由甲氧羰基的1,2-移位以及C-8位置与C-2'位置之间的键合得来的。具有中等大小保护基团的化合物得到了正常的重排产物与螺环衍生物的混合物。