Lj. Xie et al., Asymmetric alcoholysis of 2-phenyl-5(4H)-oxazolones by the catalytic mixture of cyclo[(S)-His-(S)-Phe] with chiral auxiliaries, TETRAHEDR-A, 10(24), 1999, pp. 4715-4728
Some derivatives of dipeptides containing a His residue catalyzed the ring
opening of 2-phenyl-4-benzyl-5(4H)oxazolone by methanol. The mixture of cyc
lo[(S)-His-(S)-Phe] (CHP) with chiral auxiliaries which possess both a hydr
ogen-bond donor and a hydrogen-bond acceptor was a more effective and enant
ioselective catalyst than the CHP alone. The influence of racemic and the t
wo enantiomerically pure auxiliaries on the cyclo[(S)-His-(S)Phe]-catalyzed
alcoholysis of the 5(4H)-oxazolone was different. A mixture of CHP with L-
diisopropyl tartrate catalyzed the enantioselective ring opening of 2-pheny
l-4-benzyl-5(4H)-oxazolone by methanol, ethanol and n-butanol, preferential
ly affording the N-benzoyl-L-phenylalaninates (20-39% e.e.). (C) 2000 Elsev
ier Science Ltd. All rights reserved.