Boronic ester and acid compounds, synthesis and uses

A compound having the formula (1a)

• or a pharmaceutically acceptable salt thereof;
• wherein
• P is R7—C(O)—, where R7 is heteroaryl or heteroarylalkyl;
• X2 is —C(O)—NH—;
• R is hydrogen or alkyl, or R forms together with the adjacent R1, or when A is zero, forms together with the adjacent R2, a nitrogen-containing mono-, bi- or tri-cyclic, saturated or partially saturated ring system having 4-14 ring members, that can be optionally substituted by one or two of keto, hydroxy, alkyl, aryl, aralkyl, alkoxy or aryloxy;
• R1, at each occurrence, is independently one of hydrogen, alkyl, cycloalkyl, aryl, a 5-10 membered saturated, partially unsaturated or aromatic heterocycle or —CH2—R5, where the ring portion of any of said aryl, aralkyl, alkaryl or heterocycle can be optionally substituted;
• R2 is one of hydrogen, alkyl, cycloalkyl, aryl, a 5-10 membered saturated, partially unsaturated or aromatic heterocycle or —CH2—R5, where the ring portion of any of said aryl, aralkyl, alkaryl or heterocycle can be optionally substituted;
• R3 is one of hydrogen, alkyl, cycloalkyl, aryl, a 5-10 membered saturated, partially unsaturated or aromatic heterocycle or —CH2—R5, where the ring portion of any of said aryl, aralkyl, alkaryl or heterocycle can be optionally substituted;
• R5, in each instance, is one of aryl, aralkyl, alkaryl, cycloalkyl, a 5-10 membered saturated, partially unsaturated or aromatic heterocycle or —W—R6, where W Is a chalcogen and R6 is alkyl, where the ring portion of any of said aryl, aralkyl, alkaryl or heterocycle can be optionally substituted;
• Z1 and Z2 are independently one of alkyl, hydroxy, alkoxy, or aryloxy, or together Z1 and Z2 form a moiety derived from a dihydroxy compound having at least two hydroxy groups separated by at least two connecting atoms in a chain or ring, said chain or ring comprising carbon atoms, and optionally, a heteroatom or heteroatoms which can be N, S, or 0;
• and
• A is zero.