The acylating agent (17) is then used to acylate a tricyclic benzodiazepine of formula (1) by any of the procedures described hereinbefore to yield the desired compound of formula (I), wherein A, B are CH and D, E, G, X, Y, and R4 are as defined above, R2 is hydrogen and R1 is a heterocyclic moiety selected from the (g) group of heterocycles illustrated below.