38 research outputs found
MW-enhanced high-speed deprotection of Boc group using p-TsOH and concomitant formation of N-Me-amino acid benzyl ester p-TsOH salts
A high-speed, complete deprotection of Boc group from Boc (Boc = tert-butoxycarbonyl) amino acids and protected peptide esters employing p-TsOH in toluene under microwave irradn. is found to be complete in 30 s. The deprotection can be carried out in methanol and acetonitrile also. Under the present conditions, C-peptide benzyl esters and O-benzyl ethers have been found to be stable. This has permitted us to carry out the synthesis of [Leu]enkephalin employing the Boc/Bzl-group strategy. Further more, it has been found that both Nα-Fmoc (Fmoc = 9-fluorenylmethyloxycarbonyl) and Nα-Z (Z = benzyloxycarbonyl) groups are completely stable. The present conditions can be extended for the concomitant removal of the Boc group and the formation of C-benzyl amino acid esters as well. This has been utilized for the synthesis of N-Me amino acid benzyl esters starting from Boc-N-Me amino acids in a single step
Synthesis of peptidyl ureas using p-nitrophenyl (9-fluorenylmethoxycarbonylamino)methylcarbamate derivatives
Carbamates Fmoc-NHCHRNHCO2C6H4NO2-p (Fmoc is 9-fluorenylmethoxycarbonyl, R is an amino acid side chain) were prepd. using isocyanates derived from Fmoc-amino acid azides and p-nitrophenol in the presence of an equimolar quantity of N-ethyldiisopropylamine. The carbamates were coupled with amino acid ester hydrochlorides to afford dipeptidyl ureas
N-Silylation of amines and amino acid esters under neutral conditions employing TMS-Cl in the presence of zinc dust
Direct synthesis of Fmoc protected amino acid hydroxamates from acid chlorides mediated by magnesium oxide
Silicon tetrachloride and phenol as Nα-t-butoxycarbonyl group deprotecting agent in solid phase peptide synthesis
Microwave assisted wolff rearrangement: A facile method for the synthesis of Fmoc-β-amino acids
Homologation of <i>α</i>-amino acids to <i>β</i>-amino acids: 9-Fluorenylmethyl chloroformate as a carboxyl group activating agent for the synthesis of <i>N<sup>α</sup>-</i> protected aminoacyldiazomethanes
2152-2158An efficient and stereospecific homologation
of urethane-protected α-amino acids to β-amino acids by Arndt-Eistert
approach using an equimolar mixture of Fmoc-/Boc-/Z-α-amino acid and 9-fluorenylmethyl
chloroformate for the acylation of diazomethane synthesizing the key
intermediates Fmoc-/Boc-/Z-α-aminoacyldiazo-methanes as crystalline
solids is described. They are then converted to the corresponding,β-amino
acids using silver benzoate/1,4-dioxane-water under microwave irradiation. All
the protected β-amino acids prepared have been obtained in good yield as
well as purity
2,4,5-Trichlorophenyl-(9<i>H</i>-fluoren-9-ylmethoxycarbonylamino)methylcarbamates: Synthesis, isolation, characterization and utility in the synthesis of dipeptidyl ureas
1046-1053An efficient synthesis of 2,4,5-trichlorophenyl-(9H-fluoren-9-ylmethoxycarbonylamino)methylcarbamates
employing isocyanates derived from several Fmoc-amino acids has been described.
All the carbamates made have been obtained as crystalline solids and are fully
characterized by IR, 1H NMR, 13C NMR and mass
spectrometry. They have been used as building blocks for the synthesis of
several dipeptidyl urea esters. The coupling of carbamates with N,O-bis[trimethylsilyl]amino
acids resulted in Fmoc-protected dipeptide urea acids in good yield as well as
purity. All the dipeptidyl urea esters and acids made have been well
characterized