Another process for the preparation of the compounds of the formula I comprises the steps of: (b1) coupling the side chain carboxylic acid of a compound of the formula Fmoc-B1--CHR97--C(O)OPG, wherein R97 is 2-hydroxycarbonylethyl and PG is a protecting group to an acid sensitive benzylalcohol type of linker attached to an amino functionalized resin; (b2) cleaving off the protecting group PG; (b3)