Enzymatic Building‐Block Synthesis for Solid‐Phase Automated Glycan Assembly

Abstract

Automated chemical oligosaccharide synthesis is an attractive concept that has been successfully applied to a large number of target structures, but requires excess quantities of suitably protected and activated building blocks. Herein we demonstrate the use of biocatalysis to supply such reagents for automated synthesis. By using the promiscuous NmLgtB‐B β1‐4 galactosyltransferase from Neisseria meningitidis we demonstrate fast and robust access to the LacNAc motif, common to many cell‐surface glycans, starting from either lactose or sucrose as glycosyl donors. The enzymatic product was shown to be successfully incorporated as a complete unit into a tetrasaccharide target by automated assembly.

Biocatalytic Approaches to Building Blocks for Enzymatic and Chemical Glycan Synthesis

“…1-Thioglycosides scarcely occur in Nature, with most members belonging to glucosinolates; however, they are routinely utilized as glycosyl donors for synthetic carbohydrate chemistry . Recently, biocatalysis was utilized to provide robust and simple access to a LacNAc thioglycoside building block for automated glycan assembly (AGA, Figure A) . First, Nm LgtB-B was shown to use lactose as an inexpensive donor of d -Gal for thiodisaccharide synthesis.…”

“…131 Recently, biocatalysis was utilized to provide robust and simple access to a LacNAc thioglycoside building block for automated glycan assembly (AGA, Figure 8A). 132 First, NmLgtB-B was shown to use lactose as an inexpensive donor ofD-Gal for thiodisaccharide synthesis. Additionally, a one-pot three-enzyme cycle whereby UDP-D-Gal was produced in situ using sucrose synthase in combination with Glc (1,4) -epimerase was investigated.…”

Recent Developments in Solid-Phase Glycan Synthesis

“…Recently, a biocatalytic approach assisted the preparation of a selectively protected N -acetyllactosamine (LacNAc) motif, which, after a few chemical manipulations, was employed in the solid-phase synthesis of a tetrasaccharide. 59 This enzymatic strategy combined the efficiency and scalability of biocatalysis with the flexibility of chemical synthesis; if implemented to a wider range of BBs, this approach could speed up SPGS significantly. For many years, BB preparation has been the rate-determining step of SPGS; rapid access to properly protected BBs will fuel the synthesis of new structures and the implementation of new solid-phase reactions.…”