13C n.m.r. spectroscopy and biosynthetic labelling with "5NInitrate and [1,2-13C]acetate proved to be valuable adjuncts to established chemical and spectroscopic methods in elucidating the structures of tenellin and bassianin as 3-scyl derivatives of 1,4-dihydroxy-5- \$-hydroxyphenyl)-2( 1H)-pyridone.