Hydrogen Bromide → HCID 86739414, compound

Participants

Reaction Steps

The HBr concentration in the debenzylating step can be used to control the final copolymer composition, even though a large molar excess of HBr is used and its concentration does not significantly change during reaction. For example, if the HBr concentration is 0.07 g/ml, the final composition of the copolymer is 29/71; whereas when the HBr concentration is 0.05 g/ml, the composition is 26/74. In the selective debenzylation of the benzyl glutamate portion of the intermediate some de-ethylation will always occur. However, it is possible to obtain the desired final copolymer composition by beginning with the appropriate intermediate. For example, 15/85 benzyl glutamate/ethyl glutamate can be deesterified (at anHBr concentration of 0.05 g/ml for 12 hours) to a 20/80 glutamic acid/ethylglutamate product containing a residual benzyl content of 0.68 mole %. In contrast, a 10/90 intermediate can be treated with 0.05 g/ml HBr for 24 hours to yield 20/80 glutamic acid/ethyl glutamate with an approximate residual of 0.03 mole % benzyl.

Provenance & Evidence