Dolbier HW Solutions 666

Dolbier HW Solutions 666 - 760 AMINO ACIDS, PEPTIDES, AND...

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Protect the carboxyl group of leucine as its benzyl ester. Coupling of the two amino acids is achieved by N , N -dicyclohexylcarbodiimide (DCCI)-promoted amide bond formation between the free amino group of leucine benzyl ester and the free carboxyl group of Z-protected alanine. Both the benzyloxycarbonyl protecting group and the benzyl ester protecting group may be removed by hydrogenolysis over palladium. This step completes the synthesis of Ala-Leu. 27.18 As in the DCCI-promoted coupling of amino acids, the f rst step is the addition of the Z-protected amino acid to DCCI to give an O -acylisourea. This O -acylisourea is attacked by p -nitrophenol to give the p -nitrophenyl ester of the Z-protected amino acid. 27.19 To add a leucine residue to the N terminus of the ethyl ester of Z-Phe-Gly, the benzyloxycarbonyl protecting group must f rst be removed. This can be accomplished by hydrogenolysis. C 6 H 5 CH 2 OCNHCHCNHCH 2 COCH 2 CH 3 H 2 NCHCNHCH
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This note was uploaded on 10/03/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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