End-Capped Absorbable Polymers

Poly(lactone-co-trimethylene carbonates) containing photocurable coumarin ester end groups have been prepared which are crosslinkable upon irradiation with ultraviolet light by a [2 -I- 2] cycloaddition. These materials are useful in the preparation of in vivo implants. 

A mixture consisting of 7-hydroxycoumarin (0.125 mol), K2CO3 (0.179 mol), ethyl bromoacetate (O.lSOmol), and 450 ml of acetone were refluxed for 2 hours and then filtered. The mixture was concentrated, the residue re-crystallized from ethanol, dried, and the product was isolated in 89% yield. 

The Step 1 product (27.9 mmol), 280 ml of 1,4-dioxane, and NaOH (0.405 mol) were stirred overnight at ambient temperature then acidified with 12 M HCl. The mixmre was extracted into a mixmre of CCI3H and methanol and then concentrated by distillation under reduced pressure. The residue was re-crystallized from ethanol, and the product was isolated in 90% yield. 

The Step 2 product (17.1 mmol) and thionyl chloride (0.277 mol) were refluxed 3 hours. Excess thionyl chloride was removed by distillation, and the crude product was isolated in 98% yield and used without additional purification. 

Preparation of Coumarin Ester End-Capped Poly(E-Caprolactone-co-Trimethylene Carbonate) 

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