.beta.Dribo-.epsilon.-Rhodomycinone 1-Naphthacenecarboxylic acid, 4-[(2-deoxy-.beta.-D-erythro-pentopyranosyl)oxy]-2-ethyl-1,2,3,4,6,11-hexahydro-2,5,7,12-tetrahydroxy-6,11-dioxo-, methyl ester, [1R-(1.alpha.,2.beta.,4.beta.)]- NSC271883