Page 171 - Cascade_Biocatalysis_Integrating_Stereoselective_and_Environmentally_Friendly_Reactions

6.3 One-Pot Syntheses 147

GT-module

dTDP-sugar module dTDP UDP UDP-sugar module

SuSy-module

Scheme 6.4 One pot cascade reactions for in situ regeneration of UDP-sugars and dTDP-
deoxysugars.
In this way, three enzyme modules with five enzymes were combined for in situ
regeneration and transfer of dTDP-l-rhamnose by the promiscuous GT SorF [98,
104].
The reverse reaction of GTs was further elaborated for the formation of sugar
nucleotides. Studies of the promiscuous and mutagenized GT OleD resulted in a
broad range of UDP- and dTDP-sugars [105, 106]. Moreover, OleD was used in
a one-pot synthesis for the generation of a sugar-nucleotide and concomitant in
situ transfer onto an acceptor substrate. Also coupling of OleD with other GTs was
proven for in situ generation and transfer of diverse sugars (Scheme 6.5).

O a
R 1 X R 2 XH R 2

O
NDP
R 1
NDP

O
XH
R 3 R X
b 1 R 3
Scheme 6.5 In situ production of donor nucleotide sugars followed by transfer onto an
acceptor substrate by two (a, b) glycosyltransferases. (a) Shows the reversed GT [105].

In conclusion, the reversed reactions of GTs to synthesize sugar nucleotides will
be an interesting task for the future, when it comes to the large scale production of
complex glycans or the glycosylation of complex scaffolds.
One-pot synthesis of nucleotide sugars was also demonstrated for multi-enzyme
systems as shown for UDP-Gal [107, 108] and dTDP-2-deoxy-Glc [109]. Even some
modified sugar nucleotides were synthesized in an one-pot fashion, namely UDP-
carba-sugars based on Gal, GlcNAc, Glc, and Man [110]. The cascade involved
uridine monophosphate (UMP)-kinase and acetate kinase to generate uridine
triphosphate (UTP) as well as Glc-1-P-uridyltransferase, Gal-1-P-uridyltransferase,