The structure of camptothecin: X-ray analysis of camptothecin iodoacetate

Abstract

X-Ray crystal-structure analysis of camptothecin iodoacetate has defined the constitution and absolute stereochemistry of camptothecin, a novel leukaemia and tumour-inhibiting alkaloid from Camptotheca acuminata. The alkaloid appears to be related biosynthetically to the indole alkaloids. Crystals of the iodoacetate are orthorhombic, of space group P2₁2₁2₁, with four molecules of C₂₂H₁₇IN₂O₅ in a unit cell with dimensions a= 12·77, b= 22·70, c= 7·07 Å. The atomic co-ordinates were determined by Fourier and least-squares calculations, and the final value of R over 1257 independent reflections is 9·4%.