Ganga-Ramu Vasanthakumar

(Fluoren-9-ylmethoxy)carbonyl (Fmoc) amino acid azides: Synthesis, isolation, characterisation, stability and application to synthesis of peptides

The synthesis of Fmoc amino acid azides starting from the corresponding protected amino acid and sodium azide (NaN3) by the mixed anhydride method using isobutoxycarbonyl chloride (IBC-Cl) or by the acid chloride method is described. Isolated as crystalline solids, they are stable at room temperature, with a long shelf-life, as well as in aqueous washing operations. They are useful as coupling agents in peptide synthesis.

Direct synthesis of Fmoc protected amino acid hydroxamates from acid chlorides mediated by magnesium oxide

The synthesis of Fmoc protected amino acid hydroxamates using Fmoc-amino acid chlorides and magnesium oxide is described. The method is simple and efficient, results in complete conversion, and gives good yields and satisfactory purity.

Mw-enhanced high-speed deprotection of boc group using p-TsOH and concommitant formation of N-Me-amino acid benzyl ester p-TsOH salts

Abstract A high‐speed, complete deprotection of Boc group from Boc amino acids and protected peptide esters employing p‐TsOH in toluene under microwave irradiation 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 N α‐Fmoc and N α‐Z 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.

Microwave assisted Wolff rearrangement: A facile method for the synthesis of Fmoc-β-amino acids

The Wolff rearrangement of α-diazoketones, derived from Fmoc-α-amino acids, under no base conditions on exposure to microwave irradiation for 40 to 60 sec to Fmoc-β-amino acids with retention of configuration in good yield (91–95%) is described.

Homologation of α-amino acids to β-amino acids using Boc2O

The use of Boc2O as a coupling agent in the homologation of N-urethane protected-α-amino acid to its β-homomers by the Arndt–Eistert method is described. The homologation gives good yields without racemization. The use of Boc2O as a coupling agent not only allows the easy scale up of the process but also it is cost effective.

Synthesis of β-Amino Acids: 2-(1H-Benzotriazol-1-yl)-1,1,3,3-tetramethyluronium Tetrafluoroborate (TBTU) for Activation of Fmoc-/Boc-/Z-α-Amino Acids

Abstract A new and efficient method for the homologation of urethane protected α-amino acids to its β-homomers by the Arndt-Eistert method using TBTU as a coupling agent is described. Several Fmoc-/Boc-/Z-protected α-amino diazoketone derivatives have been obtained as crystalline solids in good yield. The method is found to be rapid and stereospecific.

Synthesis of peptides employing 9-fluorenylmethyl chloroformate as a coupling agent

The synthesis of peptides employing 9-fluorenylmethyl chloroformate(Fmoc-Cl) as a coupling agent has been described. The method is simple, efficient and rapid. All the peptides have been obtainedin good yield (70–95%). Furthermore, both the 1H NMR and the HPLC studies on Fmoc-Phg-Phe-OMe and Fmoc-D-Phg-Phe-OMe revealed that the coupling is free from racemization.

A CONVENIENT METHOD FOR THE SYNTHESIS OF β-AMINO ACIDS VIA THE ARNDT-EISTERT APPROACH USING p-TOLUENESULPHONYL CHLORIDE AS A CARBOXYLIC GROUP ACTIVATING AGENT

ABSTRACT A simple method for the synthesis of Z-/Boc-/Fmoc-protected β-amino acids by the Arndt-Eistert approach employing p-toluenesulphonyl chloride for the activation of the carboxyl group of N α-protected amino acid is described. The method is rapid and gave good yields with opitical purity.

Microwave assisted facile synthesis of amino acid benzyl ester p-toluenesulfonate and hydrochloride salts

A simple method for the synthesis of several amino acid benzyl esterp-toluenesulfonate salts from the corresponding amino acid and benzyl alcohol in presence ofp-toluenesulfonic acid accelerated with microwave irradiation is described. Under similar condition, the amino acid benzyl ester hydrochloride salts have also been obtained by using thionyl chloride instead ofp-toluenesulfonic acid in good yield and purity.

SIMPLE AND EFFICIENT METHOD FOR SYNTHESIS OF Z-/Boc-AMINO ACID AMIDES USING p-TOLUENESULPHONYL CHLORIDE

Amides of Z- and Boc protected amino acids have been prepared by using p-toluenesulphonyl chloride (TsCI) for the activation of carboxyl group. The resulting mixed carboxylic-sulphonic anhydride intermediate was treated in situ with an excess of 25 percent ammonia solution. All the amino acid amides prepared were obtained as crystalline solids in good yield and purity.