Abstract: A process for producing an optically active form of a compound of formula (I) ##STR1## wherein R.sub.1 represents hydrogen or a hydrocarbon group that may be substituted; R.sub.2 and R.sub.3 independently represent hydrogen, a hydrocarbon group that may be substituted, or a heteroaromatic group that may be substituted; X' represents a substituent comprising an esterified carboxyl group or an acylated hydroxyl group; ring A represents a benzene ring that may be substituted or a heteroaromatic ring that may be substituted; ring J' represents a 7- or 8-membered heterocyclic ring containing at most 3 hetero-atoms as ring-constituent members, which may have a further substituent or substituents in addition to R.sub.1, R.sub.2, R.sub.

Abstract: Novel antibiotic C-15003 PHM, which is produced by cultivating a microorganism belonging to the genus Nocardia and being capable of producing antibiotic C-15003 PHM, and novel C-15003 PHM acylate, which is produced by subjecting C-15003 PHM thus obtained to acylation reaction with an acylating agent, have antiprotozoan and antitumor activities.

Abstract: Antibiotic C-15003 PHO of the formula: ##STR1## wherein R.sub.1 is H, hydroxyl, alkanoyloxy, alkenylcarbonyloxy or arylcarbonyloxy; R.sub.2 is H, hydroxyl or alkanoyloxy; R.sub.3 is H or alkanoyloxy is produced by introducing a hydroxyl group into 15-position of a maytansinoid compound, and, if desired, thus obtained compound is subjected to deacylation or acylation.Antibiotic C-15003 PHO is useful as antiprotozoal or antitumor agent.

Abstract: Antibiotic C-15003 PND of the formula: ##STR1## wherein R is H or alkanoyl containing not more than 5 carbon atoms is produced by contacting a maytansinoid compound with a culture broth, inclusive of a processed matter derived therefrom, of a microorganism belonging to one of the genera Streptomyces and Chainia which is able to transform said maytansinoid compound into Antibiotic C-15003 PND.Antibiotic C-15003 PND is useful as antitumor, antifungal or antiprotozoal agent.

Abstract: Novel demethylmaytansinoids representable by the formula: ##STR1## (wherein X is Cl or H; R.sub.1 is H or acyl group) are produced from maytansinoids by means of enzymic transformation. The demethylmaytansinoids are useful as antifungal, antiprotozoal or antitumor agents.

Abstract: Novel antibiotic C-15003 PHM, which is produced by cultivating a microorganism belonging to the genus Nocardia and being capable of producing antibiotic C-15003 PHM, and novel C-15003 PHM acylate, which is produced by subjecting C-15003 PHM thus obtained to acylation reaction with an acylating agent, have antiprotozoan and antitumor activities.

Abstract: Novel Antibiotic C-15003PND, which has the formula: ##STR1## wherein R represents hydrogen, --CO--CH.sub.3, --CO--CH.sub.2 --CH.sub.3, ##STR2## is produced by cultivating a microorganism of the genus Nocardia. The Antibiotic C-15003PND wherein R is acetyl, propionyl, isobutyryl or isovaleryl is useful for an antifungal, antiprotozoal or antitumor agent and Antibiotic C-15003PND wherein R is hydrogen is useful for an intermediate thereof.

Abstract: Novel demethylmaytansinoids representable by the formula: ##STR1## [wherein X is Cl or H; R.sub.1 is H or acyl group] are produced from maytansinoids by means of enzymic transformation. The demethylmaytansinoids are useful as antifungal, antiprotozoal or antitumor agents.