Abstract: Compounds of formula (I) are inhibitors of histone deacetylase activity, and are useful in the treatment of, for example, cancers, wherein R1 is a carboxylic acid group (—COOH), or an ester group which is hydrolysable by one or more intracellular carboxyesterase enzymes to a carboxylic acid group; R2 is the side chain of a natural or non-natural alpha amino acid; Y is a bond, C(?O)—, —S(?O)2—, —C(—O)O—, —C(O)NR3—, —C(?S)—NR3, —C(?NH)NR3 or —S(?O)2NR3— wherein R3 is hydrogen or optionally substituted C1-C6 alkyl; L is a divalent radical of formula -(Alk1)m(O)n(Alk2)p— wherein m, n and p are independently 0 or 1, Q is (i) an optionally substituted divalent mono- or bicyclic carbocyclic or heterocyclic radical having 5-13 ring members, or (ii), in the case where both m and p are 0, a divalent radical of formula —X2-Q1- or -Q1-X2— wherein X2 is —O—, S— or NRA— wherein RA is hydrogen or optionally substituted C1-C3 alkyl, and Q1 is an optionally substituted divalent mono- or bicyclic carbocyclic or hetero-cyclic r

Abstract: Covalent conjugation of an alpha amino acid ester to a modulator of the activity of a target intracellular enzyme or receptor, wherein the ester group of the conjugate is hydrolysable by one or more intracellular carboxylesterase enzymes to the corresponding acid, leads to accumulation of the carboxylic acid hydrolysis product in the cell and enables improved or more prolonged enzyme or receptor modulation relative to the unconjugated modulator.

Abstract: This invention provides a method of inhibiting proliferation of tumor cells in a subject by administering to the subject an effective amount of ester and thioester compounds containing an N-formyl hydroxylamine group.

Abstract: Compounds of formula (I) wherein R4 is an ester or thioester group and R, R1, R2 and R3 are as defined in the specification, inhibit proliferation of tumor cells.

Abstract: Compounds of formula 1 wherein R4 is an ester or thioester group, and R, R1, R2 and R3 are as defined in the specification are inhibitors of rapidly dividing tumour cells.