Chihiro Yokoo

Novel epoxysuccinyl peptides Selective inhibitors of cathepsin B, in vitro

A series of new epoxysuccinyl peptides were designed and synthesized to develop a specific inhibitor of cathepsin B. Of these compounds, N‐(L‐3‐trans‐ethoxycarbonyloxirane‐2‐carbonyl)‐L‐isoleucyl‐L‐proline (compound CA‐030) and N‐(L‐3‐trans‐propylcarbamoyloxirane‐2‐carbonyl)‐L‐isoleucyl‐L‐proline (compound CA‐074) were the most potent and specific inhibitors of cathepsin B in vitro. The carboxyl group of proline and the ethyl ester group or n‐propylamide group in the oxirane ring were necessary, the ethyl ester group or the n‐propylamide group being particularly effective for distinguishing cathepsin B from other cysteine proteinases such as cathepsins L and H, and calpains.

Novel epoxysuccinyl peptides A selective inhibitor of cathepsin B, in vivo

New derivatives of E‐64 (compound CA‐030 and CA‐074) were tested in vitro and in vivo for selective inhibition of cathepsin B. They exhibited 10000–30000 times greater inhibitory effects on purified rat cathepsin B than on cathepsin H and L; their initial K 1 values for cathepsin B were about 2–5 nM, like that of E‐64‐c, whereas their initial K 1 values for cathepsins H and L were about 40–200 μM. In in vivo conditions, such us intraperitoneal injection of compound CA‐030 or CA‐074 into rats, compound CA‐074 is an especially potent selective inhibitor of cathepsin B, whereas compound CA‐030 does not show selectivity for cathepsin B, although both compounds CA‐030 and CA‐074 show complete selectivity for cathepsin B in vitro.

Aragusterol C : a novel halogenated marine steroid from an Okinawan sponge, Xestospongia sp., possessing potent antitumor activity

A novel chlorinated steroid, aragusterol C, was isolated from an Okinawan marine sponge of the genusXestospongia. The compound strongly inhibited the proliferation of KB cells in vitro, and also showed potent in vivo antitumor activity against L1210 cells in mice. The complete structure of aragusterol C was determined by spectroscopic analysis and X-ray crystallographic analysis.

Synthesis and configurational assignment of methyl 3-nitrooxypropyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)pyridine-3,5-dicarboxylate

Enantiomeric (+)- and (–)-methy3-nitrooxypropyl 1,4-dihydro-2,6-dimethyl-4-(3- nitrophenyl) pyridine-3,5-dicarboxylate 1 were synthesized by esterification of the optically active monocarboxylic acids (+)-6 and (–)-6, which are available from racemate (±)-6 by optical resolution using cinchonidine and cinchonine. The absolute configuration of the key intermediates (S)-(+)-6 and (R)-(–)-6, was also unambiguously determined by the comparison with optical active (+)- and (–)-1 derived from (R)-(–)- and (S)-(+)-7 and (+)- and (–)-6, and X-ray crystallographic analysis of bromoethyl ester (R)-(–)-8 prepared from the acid (S)-(+)-7.

Studies on cephalosporin antibiotics. VI. Synthesis, antibacterial activity and oral efficacy in mice of new 7.BETA.-((Z)-2-(2-aminothiazol-4-yl)-2-(hydroxyimino)-acetamido)-3-(substituted alkylthio)cephalosporins.

A series of new 7 beta-[(Z)-2-(2-aminothiazol-4-yl)-2-(hydroxyimino)acetamido] cephalosporins (1) having various substituted alkylthio groups at the C-3 position of the cephem nucleus were prepared and evaluated for antibacterial activity and oral absorption in rats. Of these, the cephalosporin with a cyanomethylthio group (1a) showed the greatest activity against Staphylococcus aureus and Gram-negative bacteria. Its pivaloyloxymethyl ester (6a), a representative prodrug, exhibited good in vivo efficacy in mice by oral administration. The structure-activity relationships of 1 are also presented.