Substituent and solvent effects in the 1,3-dipolar cycloadditions for synthesis of anti-influenza agent peramivir and its analog

Influenza remains a health problem to humans. Peramivir is a FDA approved anti-influenza drug targeting the virus neuraminidase. The (3 + 2) cycloaddition reaction of 2-ethylbutanenitrile oxide with the cyclopentene dipolarophile derived from Vince lactam is a key step in the conventional synthesis of peramivir. Our study showed that conducting the (3 + 2) cycloaddition reactions with either aliphatic or aromatic nitrile oxide in hexane solution provided high percentage of the desired regioisomer, and the N-substituent having electron-withdrawing property is also beneficial to the regioselectivity. This study also demonstrated an alternative synthetic pathway of (-)-peramivir and the analog having a phenyl group in place of the 3-pentyl moiety. (C) 2019 Elsevier Ltd. All rights reserved.