Figure 1. Routes for natural product glycosylation. (a) General strategy for chemical glycosylation which requires multiple orthogonal protecting group (PG) manipulations and activation strategies. (b) General biosynthetic strategy initiated by NDP-sugar formation (E₂) and followed by multienzyme functionalization before Gtf-catalyzed glycosylation. (c) General overview of the complementary glycorandomization strategies described in the text. Method A is chemoenzymatic glycorandomization: E₁, sugar anomeric kinase; E₂, nucleotidylyltransferase; Gtf, glycosyltransferase; CSL, chemoselective ligation; X can be a C, N or O nucleophile; Y refers to the site of modification via chemoselective ligation. Method B is neoglycorandomization.

Figure 2. Chemoenzymatic glycorandomization of vancomycin. (a) The application of the vancomycin GtfE and a library of NDP-sugars to generate monoglycosylated nonribosomal peptides. The corresponding β-glycosides of the highlighted phenolic hydroxyl are shown. (b) The further chemoselective diversification of 1. R₂ = H unless otherwise indicated.

Figure 3. Neoglycorandomization of the cardiac glycoside digitoxin. Each diastereomer of the methoxyamine-containing digitoxin aglycon was reacted with 39 diverse reducing sugars under mild acid-catalyzed conditions to yield a library of 78 cardiac neoglycosides.