D-Tyrosine → o-Benzyl-D-tyrosine

Participants

Reaction Steps

7,5 g of a chloromethylated styrene-divinylbenzene copolymer (Merrifield resin, 1% cross-linked) are esterified with 1.113 g of Boc-D-Tyr(Bzl)-OH (3 mmoles) by refluxing for 45 hours in 60 ml of ethyl acetate in the presence of 0.42 ml of triethylamine. The resin is separated by filtration, washed successively with ethyl acetate, ethanol and water, and dried under vacuum at 25° C. 8.09 g of Boc-D-Tyr(Bzl)-resin are obtained having an esterification degree of 0.201 mmoles of D-Tyr/g calculated on the basis of the difference between the total amount of D-Tyr derivative employed and the one remained in mother liquors and in washings (determination by UV at 276 nm). The resin is Boc-deprotected by treatment with 70 ml of TFA/CH2Cl2 1/1 for 30 minutes at room temperature; thereafter it is filtered and suspended for 30 minutes under stirring in 70 ml of 10% triethylamine in chloroform. After filtrating, washing with chloroform and drying under vacuum, the product H-D-Tyr(Bzl)-resin is obtained.

Provenance & Evidence