Takeda Chemical Industries, Inc.

Toyokazu Kishi

Naoto Hashimoto

Setsuo Harada

Takashi Iwasa

Taiki Kusaka

Maytansinoids of the formula: ##STR1## wherein R is hydrogen or alkyl of 1 to 15 carbon atoms are produced by contacting, in the presence of a carbodiimide, maytansinol with a carboxylic acid of the formula:

Matansinol 3-n-hexadecanoate

Optically active maytansinoids and maytansinoid production method

Maytansinoid compounds are produced by contacting in the presence of a carbodiimide the compound maytansinol ##STR1## with an acid of the formula: ##STR2## wherein R is lower alkyl, to yield the desired maytansinoids HAVING THE RESULTANT FORMULA: ##STR3## wherein R is lower alkyl. The maytansinoids (I) are both antifungal agents and also antitumor agents.

Method for the production of maytansinoids

A novel antibiotic B-98891, which is produced by culturing a strain of microorganisms belonging to the genus Streptomyces, shows remarkable combatting effect against microorganisms causing plant diseases. Compositions containing the antibiotic are useful for controlling diseases in plants with less undesirable side effects.

Growing community of inventors

Nara, Japan

Toyokazu Kishi