The structure of latumcidin (abikoviromycin) determined by x-ray analysis.

Sir: Latumcidin1) (abikoviromycin)2>3), C10HnINK), is an optically active antiviral antibiotic isolated from the culture broth of Streptomyces reticuli var. latumcidicus. It is highly unstable and promptly polymerizes during isolation. In 1968, A.I. Gurevich et al.^ reported the structure of abikoviromycin to be (4S, 4 aR) 5-ethylidene-2,3-dihydro-l,5-pyridine4,4a-oxide by chemical method. We have attempted to confirm the structure by nmr and X-ray analysis. In the nmr spectrum of latumcidin free base in deuteriobenzene there was some uncertainty as to the assignment of the singlet at d 3.49 as a methine proton adjacent to methylene group, and the multiplet at d 1.14. An attempt to answer these questions by decoupling study was unsuccessful. Fortunately, we could crystallize the antibiotic as the selenate. The crystal structure and absolute configuration of the selenate were determined by three-dimentional Xray analysis as follows. The selenate of latumcidin was prepared fay the treatment of latumcidin with etheral selenic acid in an acetone-ether mixture at -10°C. It was quickly coated with nail polish to prevent the decomposition. The crystals are colorless needles; C1OHU .NO-H2SeO4, M.W. 306, m.p. 121°C (dec).