Coupling in the absence of tertiary amines: II

Formate salts of amino-components obtained by acidolysis of tert. butyloxy-carbonyl-derivatives with formic acid were converted to the tetrazolate salts which in turn were acylated with active esters. Addition of a tertiary base was not necessary for ready coupling. Further improvement was achieved by using a solution of tetrazole in formic acid for the removal of the tert.butyloxy-carbonyl group.