Solid-Phase Synthesis of the Monosaccharides Using Immobilized Ene-Alkoxyallene

Abstract

Solid-phase reaction in organic synthesis is an attractive method to construct complex molecules through multi-step reactions. The solid-phase reaction has many advantages. The excess reagent can be easily washed with any solvent, and purification can only be done once after the cleavage steps of the resin separately. For these reasons, the solid-phase reaction is environmentally friendly. Carbohydrate structure is very complex. Thus, regioselectivity and stereoselectivity must be considered to install a glycosidic bond. For these reasons, synthesizing carbohydrates with a solid-phase reaction was considered a challenge. A new method of synthesizing oligosaccharides using transition metal catalysts has been developed since the last few decades. Among them, our lab developed a new synthesis method for oligosaccharide synthesis using transition metal catalysts in 2014. However, stereoselective controlled reaction using transition metal-catalyst with chiral ligand in solid-phase reaction has not been sufficiently studied In this study, to attach resin to the glycon part, we synthesized internal olefin using ether linker with a long carbon chain and did Pd-catalyzed asymmetric hydroalkoxylation. Moreover, the carbon chain linker and resin connected to the internal olefin can be separated through Ru-catalyzed Ring-Closing-Metathesis without any cleavage step the resin separately. In addition, we synthesize immobilized ene-alkoxyallene, which has never been reported before, on solid. And some monosaccharide synthesized through Pd-catalyzed asymmetric hydroalkoxylation and Ru-catalyzed Ring-Closing-Metathesis was achieved.