RES-1214-1 and -2, novel and non-peptidic endothelin antagonists, were isolated from the culture broth of a fungus, Pestalotiopsis sp. RE-1214. RES-1214-1 and -2 selectively inhibited the ET-1 binding to endothelin type A receptor (ETA receptor) with IC50 values of 1.5//m and 20/iM, respectively. RES-1214-1 and -2 inhibited the increase in intracellular Ca2+ concentration elicited by 1 nMET-1 in A10cells. Taxonomyof producing strains, fermentation, isolation, structural determination, and biochemical properties of RES-1214-1 and -2 are described. we report taxonomy of the producing strains, fermentation, isolation, structural elucidation and biochemical properties of RES-1214-1 and -2.

In the course of screening for inhibitors of the lymphocyte kinase, Lck (p56^fc), aiming at novel immunosuppressants, we isolated a novel alkaloid, lymphostin (LK6-A), from the culture broth of Streptomyces sp. KYI1783. Lymphostin was produced in a fermentation mediumsupplemented with a highly porous polymer resin, which prevented the degradation of this compound in the culture broth. Lymphostin inhibited the kinase activity of Lck with an IC50 value of 0.05jUM, and exhibited potent inhibitory activity against the mixed lymphocyte reaction (MLR) with an IC50 value of 0.009um.

Lymphostin (LK6-A), a novel immunosuppressant, was isolated from the culture broth of Streptomyces sp. KYI 1783. Lymphostin showed potent inhibitory activity against the lymphocyte kinase, Lck (p56lck). The structure of lymphostin was determined by spectroscopic methods to be a novel tricyclic aromatic alkaloid. A key feature of the structure is the pyrrolo[4,3,2-<&]quinoline moiety which is rare among natural products.We have isolated a potent immunosuppressant, lymphostin (LK6-A1}, Fig. 1 mentation, purification, and biological properties of lymphostin were reported. In this paper, we describe the details of its structure determination. Structural ElucidationThe physico-chemical properties of lymphostin are summarized in Table 1. The UVspectrum indicated the presence of a polyaromatic system. The IR spectrum suggested the existence of a secondary amide and a ketone conjugated with double bonds. The molecular formula for lymphostin was established as C16H14N4O3by the HR-FAB-MS measurement, implying twelve degrees of unsaturation in the molecule. In the *H NMRspectrum in dimethylsulfoxide-d6 (DMSO-d6), one methyl singlet (5H 2.35), one 0-methyl (t)H 3.94), three aromatic methine singlets (8H 8.14, SH 8.39, dH 8.62), and a pair ofcoupled olefmic protons (<5H 7.87, dH 7.64, J= 12.6Hz) were observed. Also observ-543 ed were two additional broad signals at <5H 8.21 (two protons) and at SH 10.14 (one proton). According to the molecular formula and the IR spectrum, they were assigned to an amino and an amide proton respectively.The 13C NMR (DMSO-d6) spectrum showed all sixteen signals and the DEPT experiments revealed the presence of two methyls, five methines and nine quarternary carbons. Direct^C-^H connectivities were established by HSQC(Heteronuclear Single Quantum Coherence) experiment. The quarternary carbons at 5C 188.7 and Sc 169.7 should be assigned to a conjugated carbonyl carbon and an amide carbonyl carbon respectively, considering the results of the UVand the IR spectra. One of the methines was assumed to be adjacent to a nitrogen atom in a pyrrol ring based on its chemical shifts (5C 145.8, <5H 8.39) and a large 1JCH

MS-444 is a novel myosin light chain kinase inhibitor, isolated from the culture broth of Micromonospora sp. KY7123. The structure of MS-444 was determined to be 5,8-dihydroxy-3methyl-(9i/)-naphtho[2,3-c]furan-4-one by means of spectral analysis.

Lymphostin (LK6-A), a Novel Immunosuppressant from Streptomyces sp. KY11783: Structural Elucidation.--(AOTANI, Y.; NAGATA, H.; YOSHIDA, M.; J. Antibiot. 50 (1997) 7, 543-545; Tokyo Res. Lab.,

RES-1214-1 and -2, Novel Non-peptidic Endothelin Type A ReceptorAntagonists Produced by Pestalotiopsis sp.-Both title compounds (I) inhibit the ET-1 binding to endothelin type A receptor with IC50 values of 1.5 µM and 20 µM, respectively. Taxonomy of producing strains, fermentation, isolation, structural determination, and biochemical properties of (I) are described. -(OGAWA, T.; ANDO, K.; AOTANI, Y.; SHINODA, K.; TANAKA, T.; TSUKUDA, E.; YOSHIDA, M.; MATSUDA, Y.; J.

Structure Determination of MS-444: A New Myosin Light ChainKinase Inhibitor.--(AOTANI, Y.; SAITOH, Y.; J. Antibiot. 48 (1995) 9, 952-953; Tokyo Res. Lab.,