Method for controlled polymerization of o-carboxy anhydrides derived from α-hydroxy acids

A poly(ct-hydroxy acid) of formula (VI)

• wherein
• R1 and R2 either identical or different, independently of each other, represent a radical selected from the group consisting of
• hydrogen.
• C1-C12 alkyl radicals
• C7-C20 aralkyl radicals,
• C3-C14 cycloalkyl radicals,
• C2-C14 heterocycloalkyl radicals.
• C6-C14 aromatic radicals, and
• C3-C14 heteroaromatic radicals,
• or R1 and R2 form together a radical selected from the group consisting of C4-C14 cycle and fused C3-C14 heterocycle;
• X represents a heteroatom selected from the group consisting of O, N and S, and Z represents a C1-C12 alkyl radical;
• or
• -X-Z represents a polymer selected from the group consisting of poly(glycolic acids), poly(lactic acids), and their copolymers, said polymers being terminated by a radical -X′-Z′ wherein X′ represents a heteroatom selected from the group consisting of O, N and S, and Z′ represents a C1-C2 alkyl radical;
• R3 represents a O-protective group or a hydrogen atom n is larger than or equal to 1.

OCA of formula IV:

• wherein
• t is an integer between 1 and 10;
• A represents a heteroatom selected from the group consisting of O, N and S and a —COO and —NH radical,
• B represents a group protecting A;
• u is 1 or 2
• R2 represents a radical selected from the group consisting of
• hydrogen,
• (CH2)t-A-(B)u wherein
• t is an integer between 1 and 10,
• u is 1 or 2,
• A represents a heteroatom selected from the group consisting of O, N and S and a —COO and —NH radical,
• B represents a group protecting A;
• C1-C12 alkyls,
• C7-C20 aralkyls,
• C3-C14 cycloalkyls,
• C2-C14 heterocycloalkyls,
• aromatic C6-C14 radicals, and
• heteroaromatic C3-C14 radicals,
• and their addition salts, their isomers, enantiomers, diastereoisomers and their mixtures.