Photoreactions involving N,N-dimethylated α-amino acid salts and N-methylphthalimide are dominated by photoreduction and acetone trapping. Only, N-phenyl glycinate underwent photodecarboxylative addition in a moderate yield of 30%. In contrast, N-acylated α-amino acid salts readily gave addition products in fair to high yields of 20–95%. Comparison experiments with N,N-dimethylacetamide and amino-/amido-containing
Asymmetric synthesis of bicyclic α-amino acids by a Diels–Alder reaction to a new chiral α,β-didehydroalanine derivative
作者:Rafael Chinchilla、Larry R Falvello、Nuria Galindo、Carmen Nájera
DOI:10.1016/s0957-4166(99)00061-0
日期:1999.3
A new chiral cyclic alpha,beta-didehydroalanine derivative, (6S)-6-isopropyl-3-methylene-5-phenyl-3,6,dihydro-2H-1,4-oxazin-2-one, has been prepared by in situ aminomethylation-elimination of a chiral glycine-derived precursor. This oxazin-2-one acts as a reactive dienophile ire highly diastereoselective Diels-Alder reactions with cyclopenta- and cyclohexadiene. The major cycloadducts have been isolated and hydrolyzed to afford enantiomerically pure (-)-endo-2-aminobicyclo[2.2.1]heptane-2- and exo-2-aminobicyclo[2.2.2]octane-2-carboxylic acids. (C) 1999 Elsevier Science Ltd. All rights reserved.
Bimane cyclic esters, possible stereologues of trypanothione as antitrypanosomal agents. Bimanes 29
Tricyclic esters derived from bimanes have been synthesized with ring sizes near or equal to that of trypanothione disulfide (T(S)(2)), a bis-glutathionylspermidine that is involved in regulating the thiol status of Leishmania and other trypanosomatids. Modest activity for many of the compounds against Leishmania donovani with a maximum at the T(S)(2) ring size suggests that the esters act as T(S)(2) surrogates. However, no inhibition of T(S)(2)-reductase is observed for a number of the compounds. A series of tricyclic bimane amides with structures more closely analogous to T(S)2 are inactive in biological tests, New approaches were developed for the synthesis of the amides. The surprising effectiveness of the cyclic ester synthesis is explained. Acid chloride formation catalyzed by sulfides is briefly described.
Synthesis and pharmacological activity of 21-esters of prednisolone with glycine and glutamic acid
作者:M. I. Ryakhovskaya、G. S. Grinenko、L. M. Alekseeva、G. N. Engalycheva、V. B. Nikitin、M. É. Kaminka、R. G. Glushkov