Calicheamicins, a novel family of antitumor antibiotics. 3. Isolation, purification and characterization of calicheamicins .BETA.1Br, .GAMMA.1Br, .ALPHA.2I, .ALPHA.3I, .BETA.1I, .GAMMA.1I and .DELTA.1I.

Abstract
Novel antitumor antibiotics, calicheamicins .beta.1Br, .gamma.1Br, .alpha.2I, .alpha.3I, .beta.1I, .gamma.1I and .delta.1I were recovered from the fermentation broth of Micromonospora echinospora ssp. calichensis by solvent extraction, selective precipitation, normal phase, reversed phase and partition chromatography. The individual components were characterized by their UV, IR, 1H and 13C NMR spectral data.