Synthesis of Arabinoxylan Oligosaccharides by Preactivation-Based Iterative Glycosylations

Abstract

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Synthesis of Glucuronoxylan Hexasaccharides by Preactivation‐Based Glycosylations

“…The pentaxylan backbone will be assembled from four different xylose building blocks by the use of the preactivation‐based glycosylations. As demonstrated in our arabinoxylan syntheses, the benzoyl group will serve as a permanent protecting group for xylose hydroxy groups not involved in the glycosylations while the levulinoyl (Lev) group will function as a temporary protecting group at the position where the glucuronic acid will be installed. The benzoyl and levulinoyl groups are both ester protecting groups and thus ensure neighboring group participation in the glycosylations to form the β‐linkages.…”

“…Benzoylated thioglycosides 3 and 4 were prepared in our earlier work (Figure ) where the latter was synthesized from phenyl 1‐thio‐β‐ d ‐xylopyranoside through 2,3‐ O ‐isopropylidene and 4‐ O ‐ p ‐methoxybenzyl (PMB) protection followed by deprotection and benzoylation. The intermediate phenyl 4‐ O ‐( p ‐methoxy)benzyl‐1‐thio‐β‐ d ‐xylopyranoside ( 5 ) was selected as the starting material to prepare building block 6 with a levulinoyl and a benzoyl group at position 2 and 3, respectively (Scheme ). Attempts to perform a selective levulinoyl protection at the 2 position in 5 were unsuccessful .…”

“…We have recently presented a short synthetic strategy to prepare arabinoxylans where the xylan backbone is assembled by a preactivation‐based approach . In this protocol a protected phenyl 1‐thioxylopyranoside is activated by in‐situ‐generated p ‐nitrobenzenesulfenyl triflate and glycosylated onto a partially protected phenyl 1‐thioxylopyranoside acceptor.…”

“…In this protocol a protected phenyl 1‐thioxylopyranoside is activated by in‐situ‐generated p ‐nitrobenzenesulfenyl triflate and glycosylated onto a partially protected phenyl 1‐thioxylopyranoside acceptor. The procedure is then repeated until the desired xylan is prepared . In this way, a linear xylan backbone is assembled without using any deprotection step for each glycosylation reaction , .…”

“…The procedure is then repeated until the desired xylan is prepared . In this way, a linear xylan backbone is assembled without using any deprotection step for each glycosylation reaction , . We envisioned that the strategy could be extended to the synthesis of glucuronoxylans by coupling a glucuronic acid to the xylan backbone.…”