C-glycosylated pyrroles and their application in dipyrromethane and porphyrin synthesis

Pyrrole C-glycosylated in either the 2- or the 3-position could be prepared by the acid-catalyzed reaction between trichloroacetimidate glycosyl donors and pyrrole, or N-phenyl-trifluoroacetimidate glucosyl donor and N-TIPS pyrrole, respectively. Pyrroles carrying glucose, mannose, galactose and lactose in the 2-position, and glucose in the 3-position were obtained. The configurations of the products could be assigned using a combination of 1D and 2D NMR spectroscopy. A number of undesired background reactions yielding a variety of stereo- and regioisomers were identified; in several cases these could be eliminated. Glycosylpyrroles could be incorporated into mono- and diglycosylated dipyrromethanes, a diglycosylated BODIPY dye, and a monoglycosylated Zn(II) porphyrin without damaging the sugar unit.