A regio- and stereoselective synthesis of 4-O-sulfated chondroitin di- and tetrasaccharides based on the strategy designed for the elongation of the repeating unit

4-O-Sulfated chondroitin di- and tetrasaccharide [β- -GalNAc(4-SO3)(1→4)β- -GlcA and β- -GalNAc(4-SO3)(1→4)β- -GlcA(1→3)β- -GalNAc(4-SO3)(1→4)β- -GlcA] were regio- and stereoselectively synthesized based on the synthetic route suitably designed for the elongation of the repeating unit. Abstract 4-O-Sulfated chondroitin di- and tetrasaccharide [β- -GalNAc(4-SO3)(1→4)β- -GlcA and β- -GalNAc(4-SO3)(1→4)β- -GlcA(1→3)β- -GalNAc(4-SO3)(1→4)β- -GlcA] were regio- and stereoselectively synthesized based on the synthetic route suitably designed for the elongation of the repeating unit. Abstract Several photolabile analogs of sirolimus (rapamycin) have been synthesized. These molecules were active in a mitogen induced thymocyte proliferation assay. Two of these analogs were equipotent to sirolimus in a murine model of allograft transplantation and were shown to bind the sirolimus effector protein. These photolabile analogs will be of importance to study immunosuppressive mechanism of sirolimus.