Synthesis of azido derivatives of semotiadil, a novel 1,4-benzothiazine calcium antagonist, for photoaffinity probes of calcium channels

Aliphatic and aromatic azido derivatives of semotiadil (1), a novel calcium antagonist with a 1,4-benzothiazine skeleton, were synthesized for developing photoaffinity probes of L type calcium channels. The azidophenoxy derivative 12proved to be a potent calcium antagonist and its [3H]-labeled compound 16 would be a useful tool to clarify the binding sites of 1 to the calcium channels.