Abstract: 4-methyloxybenzyloxycarbonyl (Moz) is used to protect the alpha amino groups of the amino acids used in solid-phase synthesis of thymosin .alpha..sub.1. It was found that the Moz group can be removed rapidly and completely with 5-10% trifluoroacetic acid in CH.sub.2 Cl.sub.2. Some advantages of utilizing Moz-amino acids over Boc-amino acids in solid-phase peptide synthesis are higher yields and purities with reduced consumption of trifluoroacetic acid during the acidolytic cleavage of the N.sup..alpha. -Moz groups. Further improvements with respect to the recovery and recycling of the used solvent are obtained by using tributylamine in place of triethylamine as the neutralization agent making it possible to distill methylene chloride from the liquid waste without contamination by the lower boiling triethylamine. Methylbenzhydrylamine resin is the preferred resin support. Cleavage from the resin support and deprotection of the protected side groups of the protected thymosin .alpha..sub.

Abstract: 4-methyloxybenzyloxycarbonyl (Moz) is used to protect the alpha amino groups of the amino acids used in solid-phase synthesis of thymosin .alpha..sub.1. It was found that the Moz group can be removed rapidly and completely with 5-10% trifluoroacetic acid in CH.sub.2 Cl.sub.2. Some advantages of utilizing Moz-amino acids over Boc-amino acids in solid-phase peptide synthesis are higher yields and purities with reduced consumption of trifluoroacetic acid during the acidolytic cleavage of the N.sup..alpha. -Moz groups. Further improvements with respect to the recovery and recycling of the used solvent are obtained by using tributylamine in place of triethylamine as the neutralization agent making it possible to distill methylene chloride from the liquid waste without contamination by the lower boiling triethylamine. Methylbenzhydrylamine resin is the preferred resin support. Cleavage from the resin support and deprotection of the protected side groups of the protected thymosin .alpha..sub.

Abstract: Thymosin .alpha.1 and other peptide amides are synthesized in the solid phase using methylbenzhydrylamine resin as the support and hydrogen bromide as the deprotecting and cleaving agents. The N-terminal 14 amino acid partial sequence of thymosin .alpha.1, Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-OH is synthesized on benzyl ester resin. Using a mixture of hydrogen bromide, anisole and thioanisole as the cleavage and deprotection composition, the yields of the cleaved peptide and the selectivity of the deprotection is highly improved. For example, yields of thymosin .alpha.1 have been increased by about 90% as compared to the use of hydrogen bromide alone. By using hydrogen bromide rather than hydrogen fluoride, the synthesis can use conventional laboratory glassware and the synthesis can be easily scaled up to commercial production.