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Synthesis of non-natural ManNAc analogs for the expression of thiols on cell-surface sialic acids


The sialic acid biosynthetic pathway in mammalian cells utilizes N-acetyl-D-mannosamine (ManNAc) as a natural metabolic precursor and has the remarkable ability to biosynthetically process non-natural ManNAc analogs. Herein, we describe a recipe-style protocol for the synthesis of the novel peracetylated analog Ac5ManNTGc (1) that contains a pendant acetylthio- group and enables incorporation of thiol functionalities into the glycocalyx of living cells. We also describe the synthesis of the oxygen analog Ac5ManNGc (2), which serves as an appropriate control compound for biological experiments with 1. Both 1 and 2 were prepared from a reported, common intermediate 8, which is selectively acetylated at the hydroxyl groups. In contrast to previous methods, this synthetic approach introduces O-acetyl groups first, followed by N-acylation. Starting from the commercially available D-mannosamine hydrochloride (5), gram quantities of both 1 and 2 can be prepared over five steps in about 2–3 weeks.

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Figure 1: Synthesis of non-natural ManNAc analogs.
Figure 2: Uptake and metabolic response to peracetylated ManNAc.


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We gratefully acknowledge the funding from the Whitaker Biomedical Engineering Institute, Arnold and Mabel Beckman Foundation, the National Institutes of Health (1R01CA112314-01A1) and the National Science Foundation (QSB-0425668).

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Correspondence to Kevin J Yarema.

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Sampathkumar, SG., Li, A. & Yarema, K. Synthesis of non-natural ManNAc analogs for the expression of thiols on cell-surface sialic acids. Nat Protoc 1, 2377–2385 (2006).

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