Studies on Amino Acids and Peptides, 13 Improved Synthesis of 5‐Thioxo‐L‐proline and of Some N‐Acyl and S‐Alkyl Derivatives as Building Blocks in Peptide Synthesis
Abstract:We herein report an improved synthetic pathway to 5‐thioxo‐L‐proline (2) (using R,S nomenclature, the L form here possesses the S configuration). Compound 2 is synthesized from naturally occurring 5‐oxo‐L‐proline (1) at room temperature with 2,4‐bis(4‐methoxyphenyl)‐1,3,2,4‐dithiadiphosphetane 2,4‐disulfide (3) (Lawesson′s reagent, LR). The synthesis is an improved version of our previously published method. The optical purity of 2 has been proven by thin‐layer chromatography based on chiral ligand exchange. T… Show more
“…A number of graduate students with synthetic thiopeptide projects centered on 5-thioxo-L-proline (for which an improved synthetic procedure was developed) [147] were 'inherited' on my Å rhus colleague Sven-Olov Lawesson's untimely death in 1985. These projects were by and large completed along the lines laid down upon their conception in the Lawesson group [147][148][149][150][151].…”
Section: Thiopeptidesmentioning
confidence: 99%
“…These projects were by and large completed along the lines laid down upon their conception in the Lawesson group [147][148][149][150][151]. For instance, in one of the projects 5-thioxo-L-proline was used as the N-terminal of a series of melanocyte stimulating hormone-inhibiting factor analogs [151].…”
“…A number of graduate students with synthetic thiopeptide projects centered on 5-thioxo-L-proline (for which an improved synthetic procedure was developed) [147] were 'inherited' on my Å rhus colleague Sven-Olov Lawesson's untimely death in 1985. These projects were by and large completed along the lines laid down upon their conception in the Lawesson group [147][148][149][150][151].…”
Section: Thiopeptidesmentioning
confidence: 99%
“…These projects were by and large completed along the lines laid down upon their conception in the Lawesson group [147][148][149][150][151]. For instance, in one of the projects 5-thioxo-L-proline was used as the N-terminal of a series of melanocyte stimulating hormone-inhibiting factor analogs [151].…”
“…Thioamino acids can also readily be prepared by reaction of the corresponding amino acids with LR. Larsen et al 78 transformed 5-oxo-L-proline 47 into 5-thioxo-L-proline 48 by thionation of the lactam function with LR in 1,2-dimethoxyethane (DME) at room temperature (Scheme 15). Protection of the carboxy group of 5-oxo-Lprolin is not necessary, as nucleophilic attack by the carboxy group on LR does not occur at room temperature.…”
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