Synthesis of unnatural homologues of deoxypyridinoline as possible internal standards in analytical detection of pyridinolinic cross links of collagen

Three homologues of the collagen cross-links deoxypyridinoline, differing for the length of the side chain at the aromatic nitrogen, have been efficiently synthesized as possible internal standards in the quantitative analyses of pyridinolines. The first has a one carbon shorter N-chain, while other two have a one carbon and a two carbon longer N-chains. The stereogenic centers are introduced stereoselectively using Williams’ glycine template methodology and oxazinones to generate chirality and to suitably protect the aminoacid functionality during assembly of the pyridinoline nucleus.