Conjugate addition of phenols to 2-nitrogalactal -: Synthesis of O-(2-acetamido-2-deoxygalactosyl)tyrosine

2-Nitrogalactal derivative 1 afforded 2-deoxy-2-nitrogalactopyranosides on treatment with phenol and substituted derivatives under base catalysis. Transformation of the nitro group into the amino and the acetamido groups and O-deprotection could readily be performed, thus providing aryl 2-acetamido-2-deoxygalactopyranosides 5 and 6 in high yields and with good stereoselectivities. The same reaction sequence could also be successfully applied to N-Boc-protected tyrosine methyl ester, to afford the O-galactopyranonsyl tyrosine derivative 10. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).