Concise Synthesis of the Calicheamicin Oligosaccharide Using the Sulfoxide Glycosylation Method

A short synthesis of the calicheamicin oligosaccharide is reported. All the glycosidic linkages have been constructed using the sulfoxide glycosylation reaction, demonstrating the efficacy of the method. A general method to introduce N-O glycosidic linkages in oligosaccharides has been developed and employed to construct the N-O bond that connects rings A and B. In the final step of the synthesis, the two halves of the calicheamicin oligosaccharide are coupled in a completely deprotected form. This convergent synthesis permits the rapid construction of derivatives of the calicheamicin oligosaccharide to test the importance of particular structural features in DNA binding.