Regioselective cross-coupling reactions as an entry into biologically relevant bithiazoles: First total synthesis of cystothiazole E

No problems have been encountered while using bithiazoles in Pd-catalyzed cross-coupling reactions. It was thus possible to achieve the first synthesis of cystothiazole E (1) with a Suzuki coupling of the building blocks 2 and 3 as the pivotal C-C bond-formation step (94% yield, TBDMS = tBuMe₂Si). The bithiazole 3 could be prepared very conveniently from 2,4-dibromothiazole by regioselective cross-coupling reactions.