Leptosins A B, C, D, E and F, chaetocin derivatives, have been isolated from the mycelium of a strain of Leptosphaeria sp. attached to the marine alga Sargassum tortile. Their stereostructures, with a different configuration from that of related compounds, have been elucidated by spectroscopic analyses using various 1 D and 2D NMR techniques and some chemical transformations. All the compounds showed potent cytotoxicity against cultured P388 cells, and leptosins A and C exhibited significant antitumour activity against Sarcoma 180 ascites.' 3C NMR spectra of 1 (Table 1) by distortionless enhancement by polarization transfer (DEPT) and 'H-'H and 'H-13C correlation spectroscopy (COSY) experiments and comparison with spectral data for related compounds revealed signals for two hydroxy methine groups (C-31 and C-11') linked to two quaternary sp3-hybridized carbons, two methines (C-5a and C-5'a) bearing two nitrogens and a quaternary sp3-carbon, four quaternary sp3-carbons (C-3, C-12, C-3' and C-12') each 1 x = 4

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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 13C NMR spin−lattice relaxation time (T 1) and 13C{H} NOE of the individual carbon atoms of each 2-ethylhexyl chain in an aerosol OT (AOT) molecule have been investigated in the reversed micellar state, and the segmental mobility of each 2-ethylhexyl chain has been discussed independently in connection with the chirality effect on the 13C chemical shifts. Measurements of the NOESY and ROESY spectra of an AOT molecule and cross-peak assignments have been made. In particular, for the ROESY spectrum, the cross-peaks arising from the dipole−dipole interaction have been used to discuss successfully the spatial proximity of the two 2-ethylhexyl chains. It has also been found that the carbon atom having the larger 1/ values provides larger secondary splitting of the 13C chemical shift. Furthermore, the dipole−dipole interaction between the H3 or H3‘ protons and other specific protons has been found to be strongly dependent on the diastereoisomers. Selective NOE measurements were also made, and the proximity of intermolecular or intramolecular two 2−ethylhexyl chains has been discussed.