A novel plant growth regulator, pironetin was isolated from the culture broth of Streptomyces sp. NK10958. The structure of pironetin was determined to be (S^^^-S-ethyl-S^-dihydro^-CC^)-(2JR,3 ,S,4i?, 5(S)-2-hydroxy-4-methoxy-3, 5-dimethyl-7-nonenyl] -2H-pyran-2-one by FAB-MS,^and 13C NMR,COSY,COLOC,DEPT, IR, X-ray crystallographic analyses and adapted Mosher's method.Pironetin ( Fig. 1) is a new microbial secondary metabolite having the activity of shortening of plant height. The taxonomy, production, isolation and preliminary characterization of pironetin were reported previously1*. In this paper we describe the structural elucidation.
Results and DiscussionThe IR spectrum of pironetin (Fig. 2) showed major absorptions at 3511, 2966, 1728 cm" 1 indicating hydroxyl group, C-H bonds and a,/?-unsaturated (5-lactone, respectively. The high resolution positive ion FAB-MSof pironetin was recorded as 325.2386, which correspond to C19H33O4 (calcd 325.2379; M + H).The XHNMRand 13C NMRspectra of pironetin are shown in Figs. 3 and 4, respectively. Chemical shifts and DEPT data in the NMRspectra are shown in Table 1. The 13C NMRspectrum, 13C-XH COSY and DEPTexperiments revealed the presence of nineteen carbon signals, which were attributed to four methyl, one methyloxy, three methylene, three methine, three oxy methine, four olefinic methine, and one carbonyl carbons.Pironetin has one hydroxyl residue (5 3.45) at C-7 (5 67.3) oxy methine carbon because one acetyl group has been derived by the acetylation with Ac2O in pyridine according to NMRand IR data (data not shown).