Unexpected occurrence of prolylhydroxyproline during the analysis of collagen-bound carbohydrates by gas-liquid chromatography

Elucidation of a Sequential Iminium Ion Cascade Reaction Triggered by a Silica Gel-Promoted Aza-Peterson Reaction

In a recent methodological study investigating the synthesis of N-alkoxyazomethine ylides, an unexpected aminal byproduct was generated during our attempt to isolate O-benzyl-N-((trimethylsilyl)methyl)hydroxylamine. After a strategic investigation, silica gel was discovered to be the cause of the byproduct formation. Through the mechanistic insight from control and trapping experiments, we propose the formation of a methaniminium ion via a novel aza-Peterson reaction, which ultimately triggers a sequential iminium ion cascade sequence. Herein, we discuss the elucidation of this cascade reaction mechanism and the constraints for the byproduct formation.

A hydroxyproline-containing glycopeptide released from the walls of sycamore tissue-culture cells by hydrazinolysis

Degradation of the sycamore cell wall by hydrazinolysis yielded soluble glycopeptides. The peptide portion of the predominant glycopeptide was shown to be cyclic (4-trans-hydroxy-l-prolyl)-4-trans-hydroxy- l-proline. From this structure and the composition of the major glycopeptide it was deduced that only short oligosaccharides are attached to the hydroxyprolyl residues of the wall glycoprotein. Detailed evidence for the structure of the peptide is given in a supplementary paper that has been deposited as Supplementary Publication SUP 50020, at the National Lending Library for Science and Technology, Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1973) 131, 5.