Kuppanna Ananda

(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.

Synthesis of peptides employing Fmoc-/Boc-/Z-amino acid fluorides and activated commercial zinc dust

The coupling of urethane protected amino acid fluorides is accomplished in the presence of activated, commercial zinc dust to synthesize several di- and tripeptides. The coupling was fast and racemization free. The yield as well as purity of the peptides was satisfactory. The method was extended for the incorporation of sterically hindered α,α-dialkylamino acids and N-methylamino acids as well.

Rapid and Efficient Synthesis of Peptides Containing α,α-dialkylamino acids employing KOBt

Several Fmoc-α,α-dialkylamino acids and their acid chlorides have been prepared, isolated and characterised. The synthesis of peptides containing sterically hindered dialkylamino acids has been accomplished using acid chloride/KOBt in dichloromethane. The yields as well as the purity of the peptides were satistactory.

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.

Synthesis of pentafluorophenyl, 2,4,5-trichlorophenyl and pentachlorophenyl esters of Fmoc-amino acids using Fmoc-amino acid chlorides as intermediates

The synthesis of pentafluorophenyl, 2,4,5-trichlorophenyl and pentachlorophenyl esters of Fmoc-amino acids has been accomplished via Fmoc-amino acid chlorides as intermediates. A two phase system with a mild in-organic base (3% NaHCO3) in the aqueous layer was used. The esterification reaction was clean and complete in about 2–3 hr. All the esters prepared have been obtained in good yield and are fully characterised.

A Convenient Method for the Synthesis of Cprotected Esters of Boc- / Z-α,α- Dialkylamino Acids by the Mixed Carboxylic - Carbonic Anhydride Method

The synthesis of C-protected esters of Boc- / Z-α,α-dialkylamino acids is accomplished by using alkyl / aryl chloroformate in presence of DMAP as a catalyst. The reaction proceeds through mixed carboxylic-carbonic anhydride, which was monitored by IR. The reaction was clean and complete in about 2 hr. All the esters prepared have been obtained in good yield and are fully characterized.