New techniques in biosynthetic studies using 13C nuclear magnetic resonance spectroscopy. The biosynthesis of tenellin enriched from singly and doubly labelled precursors

13 C n.m.r. spectroscopy was used for the dual purpose of assessing the relative merits of singly and doubly labelled precursors while establishing the biosynthesis of tenellin from 13C-labelled acetate, phenylalanine, and methionine; precursors in which two adjacent sites are labelled can provide superior information, and may prove useful for obtaining enrichment data at low incorporations.