Preparation of Cyclopropane Analogues of the Natural AntibioticTAN 1057 A/B

The two new analogues 2 and 3 of the natural dipeptide antibiotic TAN 1057 A/B ( 1 ), both with cyclopropyl containing β‐amino acid side chains, were prepared. The synthesis of the corresponding β‐amino acids in appropriately protected form ( 4 ‐Z 3 and 5 ‐Z 2 , respectively) from the correspondingly protected (hydroxyethyl)‐ ( 7a ) and (hydroxymethyl)‐substituted cyclopropylideneacetate ( 7b ), prepared in two steps each from homoallyl and allyl benzyl ether, respectively, was achieved in nine and seven steps, respectively, with overall yields of 17 ( 4 ‐Z 3 ) and 9.3 % ( 5 ‐Z 2 ), respectively. Coupling with the N ‐methyldihydropyrimidinone 22 and deprotection gave the compounds 2 and 3 , which turned out to be active against methicillin resistant strains of Staphylococcus aureus , albeit to a lesser extent than TAN 1057 itself. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)