4 CHEMICAL STUDIES ON NEGAMYCIN,A NOVEL HYDRAZIDE ANTIBIOTIC

Abstract

Negamycin (I, C_9H_<20>O_4N_4), found in 1969, is a new antibiotic isolated from the culture filtrate of Streptomyces purpeofuscus, demonstrating strong inhibition against resistant Gram-negative bacteria including Pseudomonas. We report the structure established on the basis of spectral data and chemical degradations, the synthetic work, and an interesting novel and acid-catalysed rearrangement of 1-methylhydrazinoacetic acid (VII) discovered during the structural study. The acid hydrolysis afforded a new δ-hydroxy-β-lysine (III), VII, 1, 2-dimethylhydrazine (V), sarcosine, and methylamine. The absolute configuration of I has been determined to be [2-{(3R, 5R)-3, 6-diamino-5-hydroxyhexanoyl}-1-methylhydrazino] acetic acid based on the optical property of the lactone derivative (IV). It has been shown that VII is converted into V along with sarcosine and methylamine, showing that a new rearrangement of VII took place in acidic condition. The protection of δ-hydroxy group of III with dihydropyran was found to be essential for the hydrazide synthesis of III and VII. The syntheses of VII and the antipode have successfully been carried out from D-galacturonic acid and 3-amino-3-deoxy-D-glucopyranose, respectively.