摘要:
A highly enantioselective metal-free synthesis of both enantiomers of Rolipram is reported. The key stereoinductive step is a cinchona alkaloid catalyzed opening of a cyclic anhydride prepared from isovanillin, where both enantiomers are available using the same chiral catalyst in two protocols. An extended one-pot Curtius sequence provides the lactam directly from the desymmetrization product after enrichment in high yield and excellent ee. (C) 2013 Elsevier Ltd. All rights reserved.