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Asymmetric Pictet–Spengler Reactions Employing N,N ‐Phthaloyl Amino Acids as Chiral Auxiliary Groups
Author(s) -
Waldmann Herbert,
Schmidt Gunther,
Henke Henning,
Burkard Michael
Publication year - 1995
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.199524021
Subject(s) - diastereomer , chemistry , pictet–spengler reaction , amino acid , enantioselective synthesis , titanium , organic chemistry , stereochemistry , catalysis , biochemistry
Both aromatic and aliphatic Schiff bases 1 can be cyclized asymmetrically in the presence of titanium alkoxides if N,N ‐phthaloyl‐protected amino acids are employed as chiral auxiliaries. The desired heterocycles 3 , which are suitable for alkaloid syntheses, are formed with diastereomer ratios of up to 99%. R n Pr, i Pr; R 1 Me, Et, i Pr, Ph, Ar; R 2 Me, i Pr, t Bu.