Sodium-liquid ammonia reduction in peptide chemistry

An easy access to two epimeric N-substituted (2S)-2-(2'-hydroxypropyl)pyrrolidines

“…10,11 Before the synthesis of 5a employing Tebbe's reagent, we also visualized to prepare ketone 5a in basic medium. For this, compound 9a was allowed to react with MeLi which furnished 5a,5b with 54% enantiomeric excess in favor of the (S) configuration.…”

Chemoselective synthesis of functional homocysteine residues in polypeptides and peptides

“…This mild process is chemoselective, tolerates a variety of functional groups, and gives excellent yields of products. Previously, M residues, mainly as the amino acid, have been converted to R-C H analogs through use of Na/NH 3 , 24 which is incompatible with some functional groups and can lead to racemization, 25 resulting in this method being rarely used for peptides. We envision our methodology for facile preparation of stable R-C H derivatives from natural M residues will provide many opportunities for creation of [15+Na] + adducts labeled.…”

Aaptamine and related products. Their isolation, chemical syntheses, and biological activity

“…115 However, submission of the mixture of alcohols and methyl ethers 142 and 143 to reaction with sodium in liquid ammonia effected the simultaneous removal of the tosyl protecting group and the benzylic oxygenated moieties, 116 furnishing the expected 2,3,3a,4,5,6-hexahydroaaptamine (38) in 83% yield, which completed the formal synthesis of the natural product.…”