Asymmetric Synthesis of Activated α-Amino Esters via Chromium Carbene Complex Photochemistry

Abstract

Optically active chromium aminocarbene complexes were α-alkylated and then photolyzed in the presence of 2,4,5-trichlorophenol to produce a number of optically active activated α-amino esters. These underwent coupling with amino acid esters or a soluble PEG-supported dipeptide to introduce the chromium−carbene-complex-derived amino acid residue into the peptide.

Synthesis and Characterization of Mono-, Di-, and Tri-Poly(ethylene glycol) Chlorin e6 Conjugates for the Photokilling of Human Ovarian Cancer Cells

“…Similar factors that make the PEGylated chlorins more soluble in 1 % (v/v) DMSO water affected their octanol/water partition coefficients. Computed log P values were obtained with the ACD algorithm, which has performed well in predicting the log P values of drugs, and PEG groups introduce steric hindrance to the sites in which they are bound . We find C log P values to decrease by about 2 orders of magnitude as the number of attached PEG groups increased from 0 to 3.…”

Photoinduced Reactions of Metal Carbenes in Organic Synthesis

“…Photoinduced Reactions of Metal Carbenes in Organic Synthesis 183 Photo-driven reactions of aminocarbenes to produce a amino acids (28) Activated esters for use in peptide-coupling reactions were produced by photolysis of optically active chromium aminocarbenes with alcohols which are good leaving groups, such as phenol, pentafluorophenol, 2,4,5-trichlorophenol, and N-hydroxysuccinimide (Table 17) [109]. Since arylcarbenes bearing the op-…”

Photoinduced Reactions of Metal Carbenes in Organic Synthesis

“…(26) (27) Photoinduced Reactions of Metal Carbenes in Organic Synthesis 183 Table 15 Photo-driven reactions of hydroxycarbene complexes with alcohols 184 L. S. Hegedus Table 16 Photo-driven reactions of aminocarbenes to produce a amino acids (28) Activated esters for use in peptide-coupling reactions were produced by photolysis of optically active chromium aminocarbenes with alcohols which are good leaving groups, such as phenol, pentafluorophenol, 2,4,5-trichlorophenol, and N-hydroxysuccinimide (Table 17) [109]. Since arylcarbenes bearing the op- tically active oxazolidine auxilliary are difficult to synthesize and often unstable, the above chemistry does not afford an effective approach to aryl glycines.…”