Importance

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Abstract

The present invention relates to a compound of formula (1), or a pharmaceutically acceptable salt thereof, wherein: Ar is a substituted aryl or heteroaryl group bearing at least one nitro or azido group or is a group of formula (2) or (3) wherein R.sub.1, and R.sub.2, which may be the same or different are independently optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, aryl, COR.sub.3 or, together with the intervening carbon atom, form an optionally substituted heterocycloalkyl or carbocyclic ring; L is --OC(O)-- or --OP(O)(OR.sub.6)--; n is 0 or 1; X is 0, S, NR.sub.7 or a single covalent bond; R.sub.3 is OR.sub.4 or NR.sub.4R.sub.5; R.sub.4, R.sub.5, R.sub.6 and R.sub.7 are each independently hydrogen or optionally substituted alkyl or, where R.sub.r is NR.sub.4R.sub.5, R.sub.4 and R.sub.5 can be joined to form, together with the intervening nitrogen atom, a heterocycloalkyl ring; R.sub.8 is hydrogen, alkoxy or dialkylaminoalkyl; R.sub.9 is optionally substituted alkyl; Rio is hydrogen, alkyl, alkoxy or dialkylaminoalkyl; R.sub.11 and R.sub.12 are independently hydrogen, alkyl, alkoxy, thioalkoxy, amino, alkylamino, dialkylamino, morpholino, piperidino, piperazino or 1=aziridinyl; A is an optionally substituted aryl or heteroaryl ring; and Dr is a moiety such that DrXH represents a cytotoxic or cytostatic compound.

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First Claim