Glycosylation significantly alters
the biological and physicochemical properties of small molecules.
β-Lactam alcohols comprise eligible substrates for such a transformation
based on their distinct relevance in the chemical and medicinal community.
In this framework, the unprecedented enzymatic glycosylation of the
rigid and highly strained four-membered β-lactam azaheterocycle
was studied. For this purpose, cis-3-hydroxy-β-lactams
were efficiently prepared in three steps by means of a classical organic
synthesis approach, while a biocatalytic step was implemented for
the selective formation of the corresponding 3-O-α-
and -β-glucosides, hence overcoming the complexities typically
encountered in synthetic glycochemistry and contributing to the increasing
demand for sustainable processes in the framework of green chemistry.
Two carbohydrate-active enzymes were selected based on their broad
acceptor specificity and subsequently applied for the α- or
β-selective formation of β-lactam-sugar adducts, using
sucrose as a glucosyl donor.
In view of the global pandemic of obesity and related metabolic diseases, there is an increased interest in alternative carbohydrates with promising physiochemical and health-related properties as a potential replacement for traditional sugars. However, our current knowledge is limited to only a small selection of carbohydrates, whereas the majority of alternative rare carbohydrates and especially their properties remain to be investigated. Unraveling their potential properties, like digestibility and glycemic content, could unlock their use in industrial applications. Here, we describe the enzymatic production and in vitro digestibility of three novel glycosides, namely, two kojibiose analogues (i.e., D-Glc p -α-1,2-D-Gal and D-Glc p -α-1,2-D-Rib) and one nigerose analogue (i.e., D-Glc p -α-1,3-L-Ara). These novel sugars were discovered after an intensive acceptor screening with a sucrose phosphorylase originating from Bifidobacterium adolescentis (BaSP). Optimization and upscaling of this process led to roughly 100 g of these disaccharides. Digestibility, absorption, and caloric potential were assessed using brush border enzymes of rat origin and human intestinal Caco-2 cells. The rare disaccharides showed a reduced digestibility and a limited impact on energy metabolism, which was structure-dependent and even more pronounced for the three novel disaccharides in comparison to their respective glucobioses, translating to a low-caloric potential for these novel rare disaccharides.
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