Biosynthesis of ursolic acid in cell cultures of Perilla frutescens Britt. var. acuta Kuda: mechanism of D- and E-ring formation
13 C N.m.r. analysis of ursolic acid produced by cultivation of Perilla frutescens Britt. var. acuta Kudo in the presence of [3,5-13C2]- and [4-2H2,2-13C]-mevalonolactone verified two backbone rearrangements and a 1,2-hydride shift with regard to formation of the D-and E-ring during biosynthesis of ursolic acid.