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The structure of the antibiotic micrococcin P has been determined by 13C n.m.r. spectroscopy. IN earlier r e p ~r t s , l -~the structure of subunits A, B, C, D, and E (Figure ) of the antibiotic micrococcin Pl was established. We now demonstrate, on the basis of 13C n.m.r. spectroscopy, the presence of one molecule of subunits A, C, D, and E and two molecules of subunit B per molecule of the antibiotic and revise the constitution of subunit E. Furthermore, we show that these fragments account for the total composition of micrococcin P (1) and establish its complete structure.The noise-decoupled 13C n.m.r. spectrum of micrococcin P (l), recorded in (CD,),SO solution on a Rruker HX-360 spectrometer operating at 90.52 MHz, exhibits 48 signals.

The structures of cervinomycins Ax (1) and A2 (2), a potent anti-anaerobic and antimycoplasmal antibiotic were investigated by means of recent NMR techniques of 0-methyl ether (3) and C,O-dimethyl ether (4) obtained by methylation of 2 with CH3I in the presence ofAg2O.The antibiotic 2 posesses a polycyclic structure involving a xanthone skeleton. The structure of 1 was confirmed to be a hydroquinone of 2 from the evidences that oxidation of 1 with Ag2Oand acetylation of 1 with (CH3CO)2Oin pyridine afforded quantitatively 2 and triacetylcervinomycin Ax (7), respectively.Cervinomycin is an anti-anaerobic and anti-mycoplasmal antibiotic produced by Streptomyces cervinus sp. nov.0 The antibiotic posesses a novel xanthone skeleton2) and consists of two components, Ax (1), mp (dec) >240°C, C29H23NO9 and A2 (2), mp (dec) >290°C, C29H21NO9 which are barely soluble in most solvents. Both components and their acyl derivatives afforded a monocrystal in appropriate solvents, however the X-ray crystallographic analyses were unsuccessful because of extreme instability of the crystals on exposing to air. Therefore, NMRspectroscopic analysis was carried out for cervinomycin methyl derivatives. In this paper we wish to report the structure elucidation of cervinomycin by means of NMRspectroscopy. 2 and 183.2). These data suggest that cervinomycin has a conjugated poly-

The origin of the skeletal carbons in the lactone ring of 16-membered macrolide antiobiotics has been studied. 13C-labeled antibiotics leucomycin and tylosin, have been obtained from the culture broth of Streptomyces kitasatoensis 66-14-3 and Streptomyces fradiae C-373, respectively in the presence of appropriate 13C-labeled precursors, and 13C NMR spectra of the antibiotics thus obtained have been measured. It was shown that the aglycone of leucomycin A3 is derived from five acetates, one propionate, one butyrate, and an unknown precursor corresponding to two carbons. The formyl carbon which is characteristic of the basic 16-membered macrolides orginates from C-4 butyrate. On the other hand, the aglycone of tylosin is formed from two acetates, five propionates and one butyrate. Butyric acid and ethylmalonic acid are metabolized to propionyl-CoA or methylmolonyl-CoA through a pathway involving methylmalonyl-CoA mutase, and subsequently incorporated into the lactone ring of tylosin.