Anionic Oxidation of Simple Alkyl Aromatics

ChemInform Abstract: TRYPSIN INHIBITORS. I. SYNTHESIS OF PROTECTED PEPTIDES RELATED TO SEQUENCE 1‐10 OF PORCINE PANCREATIC SECRETORY TRYPSIN INHIBITOR II (KAZAL)

“…The ensuing dipeptide (A-VII) was partially deprotected by catalytic hydrogenolysis and the resulting free base (A-VIIa) was acylated with a-1 -succinimidyl-y-terr-butyl benzyloxycarbonylglutamate (74,75). The tripeptide A-VIII was catalytically hydrogenated and acylated with the azide prepared from benzyloxycarbonylthronylserine hydrazide (77,78) to give the protected pentapeptide benzyloxycarbonylthreonylseryl-y-tert-butylglutamylvalylserine tert-butyloxycarbonylhydrazide o-Nitrophenylsulfenylthreonyl-S-acetamidomethylcysteine (A-X), obtained by acylation of S-acetamidomethylcysteine (71, 72) with 1 succinimidyl o-nitrophenylsulfenylthreoninate (79) was reacted by the DCC-HOBt procedure (47,48) with the pentapeptide free base threonylseryl-y-tert-butylglutamylvalylserine tert-butyloxycarbonylhydrazide (A-IXa) obtained by catalytic hydrogenation of A-IX, to give thechromato-(A-IX).…”

Metal‐Stabilized C‐Protonated Diazomethane: A Methanediazonium Complex

“…Addition of an excess of diazomethane ( I ) at -85°C to a THF solution of cyclopentadienyltricarbonyltungsten hydride (2) followed by a gradual raising of the temperature to +25"C affords a dark red neutral compound (3) which can be isolated by column chromatography. Compound (3) is extremely air-sensitive in solution, and slowly decomposes with evolution of gas when heated to above its melting range of 36-39°C in a sealed tube.…”

SN 1 and SN 2 mechanisms for the deprotection of synthetic peptides by hydrogen fluoride

“…The different behavior of the alkylation reaction in TFA and HF has led t o many practical procedures t o minimize these side reactions. They include: 1) reduction of nucleophilicity of the amino acid side chains by incorporating methionine sulfoxide for methionine (18)(19)(20)(21) and N' -formy1 tryptophan (22)(23) for tryptophan and 2) addition of carbocation scavengers such as anisole (24), phenolic compounds (24-27) and sulfide (8, 9,28). In general, these measures are quite effective in reducing the t-butylation side reaction, particularly in TFA, and are often incorporated into the normal peptide synthesis protocol; however, the C-benzylation side reaction of tyrosine remains largely unresolved and poorly understood.…”