| abstract |
A process for preparing compounds of the formula Iin whichR is hydrogen, C1-C6-alkoxy, -NHC1-C6-alkyl, -N(C1-C6-alkyl)2, OH, NH2R1 is hydrogen, C1-C6-alkyl, Me3Si, C1-C6-alkyl-SR2 is Boc, C1-C6-acyl, mesyl, benzenesulfonyl, tosyl, trifluoroacetyl, A1-A3-peptiden is 1, 2R4 is H, C1-C6-alkyl,is described. |