title: Application of empirical design methodologies to the study of the influence of reaction conditions and N-alpha-protecting group structure on the enzymatic X-Phe-Leu-NH(2) dipeptide synthesis in buffer/dimethylformamide solvents systems.
abstract: The influence of five different N-terminal protecting groups (For, Ac, Boc, Z, and Fmoc) and reaction conditions (temperature and dimethylformamide content) on the alpha-chymotrypsin-catalyzed synthesis of the dipeptide derivative X-Phe-Leu-NH(2) was studied. Groups such as For, Ac, Boc, and Z always rendered good peptide yields (82% to 85%) at low reaction temperatures and DMF concentrations, which depended on the N-alpha protection choice. Boc and Z were the most reactive N-alpha groups and, in addition, the most suitable for peptide synthesis. On the other hand, the use of empirical design methodologies allowed, with minimal experimentation and by multiple regression, to deduce an equation, which correlates the logarithm of the first order kinetic constant (log k') with reaction temperature, DMF concentration, and hydrophobicity (log P values) of the different protecting groups. The predictive value of the equation was tested by comparing the performance of another protective group, such as Aloc, with the performance predicted by said equation. Experimental and calculated k' values were found to be in good agreement.
authors.affiliation: Unit for Peptide Chemistry and Biochemistry (C.I.D.) (CSIC), Jordi Girona, Barcelona, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Calvet
authors.forename: P
authors.initials: P
authors.lastname: Clapés
authors.forename: J P
authors.initials: JP
authors.lastname: Vigo
authors.forename: N
authors.initials: N
authors.lastname: Xaus
authors.forename: X
authors.initials: X
authors.lastname: Jorba
authors.forename: R M
authors.initials: RM
authors.lastname: Mas
authors.forename: J L
authors.initials: JL
authors.lastname: Torres
authors.forename: G
authors.initials: G
authors.lastname: Valencia
authors.forename: M L
authors.initials: ML
authors.lastname: Serralheiro
authors.forename: J M
authors.initials: JM
authors.lastname: Cabral
authors.forename: J M
authors.initials: JM
authors.lastname: Empis