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Bifunctional 2,5‐Diketopiperazines as Efficient Organocatalysts for the Enantioselective Conjugate Addition of Aldehydes to Nitroolefins
Author(s) -
Durini Marco,
Sahr Florian A.,
Kuhn Michael,
Civera Monica,
Gennari Cesare,
Piarulli Umberto
Publication year - 2011
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201100794
Subject(s) - chemistry , bifunctional , enantioselective synthesis , diketopiperazines , conjugate , stereoselectivity , organocatalysis , combinatorial chemistry , stereochemistry , furan , michael reaction , enamine , catalysis , organic chemistry , mathematical analysis , mathematics
Four peptidomimics ( 3 – 6 ) containing the cis ‐ DKP‐1 or trans ‐ DKP‐2 scaffolds and either L ‐Pro or D ‐Pro were synthesized. DKP‐1 and DKP‐2 are bifunctional diketopiperazines formally derived from the head‐to‐tail cyclization of L ‐aspartic acid and either ( R )‐ or ( S )‐2,3‐diaminopropionic acid, which feature aminomethyl and carboxymethyl side arms in the 3‐ and 6‐positions of the 2,5‐piperazindione ring. Peptidomimics ( 3 – 6 ) were tested as organocatalysts in the conjugate addition of several aldehydes to β‐nitrostyrene and ( E )‐2‐(furan‐2‐yl)nitroethene with good to excellent diastereo‐ and enantioselectivities. Monte Carlo/Energy Minimization (MC/EM) conformational searches were performed on the four catalysts and their enamine derivatives with propanal to rationalize the observed stereoselectivity.