Abstract: The present invention relates to an improved process for the preparation of N6-(aminoiminomethyl)-N2-(3-mercapto-1-oxopropyl)-L-lysylglycyl-L-?-aspartyl-L-tryptophyl-L-prolyl-L-cysteinamide, cyclic(16)-disulfide of formula (1), which involves assembling a peptide chain comprising of six amino acids and a thioalkyl carboxylic acid in a required sequence on a solid support to obtain a peptide bound resin of formula (2), capping the free amino groups after each coupling, cleaving Dde group in the peptide of formula (2) from the solid support to obtain peptide-solid support of formula (3), guanylating the peptide of formula (3) at ?-lysine-NH2 in an organic solvent to obtain peptide-solid support of formula (4), cleaving and deprotecting all groups in the peptide of formula (4) from the solid support to obtain peptide-amide formula (5), oxidizing the SH-peptide of formula (5) with an appropriate oxidizing agent to obtain the crude peptide-amide of formula (1) and purifying the crude peptide-amide of formula (1) b