Simple, inexpensive, and facile l-prolinamide used as a recyclable organocatalyst for highly efficient large-scale asymmetric direct aldol reactions
作者:Jiangwei Xu、Xiangkai Fu、Chuanlong Wu、Xiaoyan Hu
DOI:10.1016/j.tetasy.2011.05.008
日期:2011.4
In order to discover a simple, inexpensive, and efficient route to obtain highly enantiomerically enriched anti-aldol products for applications in industry, a series of prolinamides 1-5 with different carbocyclic rings have been synthesized from achiral cycloalkylamine, and prolinamides 6-9 have been synthesized from aniline with different substituents. The organocatalysts obtained catalyzed the asymmetric aldol reaction and showed that no matter carbocyclic rings or aromatic rings were found to play a significant role in the formation of the aldol products. Moreover, the prolinamide 6 exhibited efficient catalytic activity in the asymmetric aldol reaction only with 5 mol % catalyst loading and 4 equiv of ketone, and afforded aldol products in high diastereoselectivity (up to anti/syn 99:1) and enantioselectivity (99%) and significantly enhanced the reaction yield (99%). These results were much better than L-proline-3-nitroanilide which had the strongest electron-withdrawing group on the aromatic ring. Furthermore, catalyst 6 can be easily recovered and reused, without a significant decrease of enantioselectivity after five cycles. This inexpensive, simple, and recyclable catalyst can be efficiently used in large-scale reactions with the enantioselectivities being maintained at the same level, which offers a great possibility for application in industry. (C) 2011 Elsevier Ltd. All rights reserved.
Synthesis of Analogues of
<scp>BCTC</scp>
Incorporating a Pyrrolidinyl Linker and Biological Evaluation as Transient Receptor Potential Vanilloid 1 Antagonists
A series of novel pyrrolidinyl linker TRPV1 antagonists were prepared in an effort to lower the hyperthermic side‐effects of first‐generation antagonist BCTC. These compounds were investigated for antagonism of hTRPV1 activation by capsaicin and acid in vitro. Preliminary results suggested the compounds 10a, 10b, 10c and 10j had favorable TRPV1 antagonism activity. In further studies in vivo, 10b, comparable to BCTC, showed potent analgesic activity in capsaicin‐induced and heat‐induced pain models. In addition, 10b indicated a reduced risk of body temperature elevation. All of these demonstrated that 10b can be considered as a safe candidate for the further development of analgesic drugs.