Chemoenzymatic synthesis of uridine diphosphate-GlcNAc and uridine diphosphate-GalNAc analogs for the preparation of unnatural glycosaminoglycans

Abstract

Eight N-acetylglucosamine-1-phosphate and N-acetylgalactosamine-1-phosphate analogs have been synthesized chemically and were tested for their recognition by the GlmU uridyltransferase enzyme. Among these, only substrates that have an amide linkage to the C-2 nitrogen were transferred by GlmU to afford their corresponding uridine diphosphate(UDP)-sugar nucleotides. Resin-immobilized GlmU showed comparable activity to nonimmobilized GlmU and provides a more facile final step in the synthesis of an unnatural UDP-donor. The synthesized unnatural UDP-donors were tested for their activity as substrates for glycosyltransferases in the preparation of unnatural glycosaminoglycans in vitro. A subset of these analogs was useful as donors, increasing the synthetic repertoire for these medically important polysaccharides.

Figure 1

Enzymatic synthesis of UDP-GlcNAc and UDP-GalNAc analogs

Scheme 1

Synthesis of GlcNH₂-1-phosphate

Scheme 2

Synthesis of GlcNAc/GalNAc-1-phosphate

Scheme 3

Synthesis of GlcN-alkyne-1-phosphate

Scheme 4

Synthesis of GalN-alkyne-1-phosphate

Scheme 5

GlcN-TFA-1-phosphate

Scheme 6

Synthesis of GlcN-ene-1-phosphate

Scheme 7

Chemical synthesis of UDP-GlcN derivatives