Abstract: A process for the preparation of tripeptides of the general formula IU-A-B-C-OH Iin which U denotes hydrogen or a urethane protective group and A, B and C denote amino acids, by reaction of a compound of the general formula IIU'-B-OH IIin which U' is a urethane protective group which can be eliminated by hydrogenolysis, with a compound of the general formula IIIH-C-OR IIIin which R denotes alkyl, by the PPA method, elimination of U', and reacting the resulting compound of the formula IVH-B-C-OR IVwith a compound of the formula VU-A-OH Vin the presence of propylphosphonic anhydride, and finally eliminating R enzymatically.

Abstract: Process for the preparation of thiophene derivatives and also new dihydrothiophene 1-oxides.Thiophene derivatives having an--optionally substituted--amino group on the thiophene ring are prepared by dehydrogenating dihydrothiophenes, substituted in a manner identical to that of the desired thiophene derivatives, by means of H.sub.2 O.sub.2, the dihydrothiophenes being reacted with H.sub.2 O.sub.2 in a first reaction stage in a neutral medium to give the corresponding sulfoxides, which are then rearranged into the thiophene derivatives by means of acid in the second reaction stage.The dihydrothiophene 1-oxides formed as intermediates in this reaction are new compounds. Like the thiophene derivatives formed from them by rearrangement with acid, they are intermediates, mainly in the sector of plant protection agents and pharmaceuticals.