P. Hoogerhout, C. Guis, C. Erkelens
Sep 2, 2010
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Recueil des Travaux Chimiques des Pays-Bas
Abstract
The cesium salts of N-[(9-fluorenylmethoxy)carbonyl]-L-serine (Fmoc-Ser, 1a)*** and -L-threonine (Fmoc-Thr, 1b) were treated with 2-(bromomethyl)-9,10-anthraquinone (Maq-Br), yielding Fmoc-Ser-OMaq (2a, 79%) and Fmoc-Thr-OMaq (2b, 74%). HgBr2-catalyzed glycosylation with 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl bromide gave Fmoc-Ser(Ac4βGal)-OMaq (3a, 89%) and Fmoc-Thr(Ac4βGal)-OMaq 13b, 53%). Fmoc-Ser(Ac4βGal)-OH (4), obtained by reaction of 1a with Na2S2O4 (88%), was condensed with H-Ala-OMaq using the DCC/HOBt method (83%). The Fmoc-Ser(Ac4βGal)-Ala-OMaq(5), thus obtained, was Nα-deprotected with morpholine and coupled with Fmoc-Ala using water soluble carbodiimide in the presence of HOBt to yield Fmoc-Ala-Ser(Ac4βGal)-Ala-OMaq (6, 59%). The fully deprotected glycotripeptide (8) was obtained from 6 by successive treatment with Na2S2O4, morpholine and hydrazine hydrate (81%). The compounds 3a, 6 and 8 were characterized using correlated 300 MHz 1H NMR spectroscopy (2D-COSY).