Abstract
The crystal and molecular structure of anthracycline antibiotic steffimycin B(C29H320O13) has been determined by X-ray diffraction and the stereochemistry revealed. The orthorhombic crystals belong to space group P212121, with the dimensions; a = 8.253 (2), b = 8.198 (2), c = 40.850 (8) Å and Z = 4. Intensity data were collected for 2518 independent reflections. The structure was solved by direct methods and refined to an R value of 0.066 for 1410 reflections. The configuration in ring A is TR,8S,9S. Ring A adopts half chair conformation, while the sugar ring has the regular chair conformation. The molecule most probably binds to double helical DNA through intercalation and hydrogen bonding.