Application of TKasecatalyzed reaction in organic syntheses

This decarboxylation reaction serves as the tool for enzyme-mediated organic synthesis.59-61 As shown in Fig. 18, the addition of thiazolium intermediate derived

OH OH

OH O

-02cA-oh

Hydroxypyruvate

OH O

OH Product

Unreacted

OH Product from hydroxypyruvic acid proceeds via re-face attack to afford the product with stereochemically defined 2,3-erythro stereochemistry. The examples are summarized in Table 5. This method works very well for the synthesis of naturally occurring phosphorylated,4957 non-phosphorylated ketoses43 48 and deoxy sugars.3547 Moreover, 2,3-erythro-diol motif is exemplified in the chemoenzymatic synthesis of the L-series of aldoses,45 aza sugars51-53 and (±)-exo-brevicomin, an insect pheromone.54 The stereochemically controlled synthesis of aldehydes with D(2) configuration from naturally occurring amino acids has been proposed for the enhanced reactivity,58 although the C—C bond formation works even from the racemic substrate with a concomitant kinetic resolution.

TKase can be used as a tool for the kinetic resolution of racemic a-hydroxy aldehydes. For example, D-glyceraldehydes shows 66% of the rate compared with

Table 5

Transketolase-catalyzed reaction of hydroxypyruvate

"O2CA-OH

TKase

Acceptor substrate

Product

Source

Ref.

HO CHO

MeO CHO

Yeast Spinach

E. coli

Yeast Spinach

MeS CHO

OMe MeO^CHO

Cl CHO

OH OMe O

OH O

Spinach

Spinach

Spinach

Me -CHO

Yeast Spinach

Acceptor substrate

Product

Source

Ref.

Me CHO

Yeast E. coli

Spinach

Me CHO

HO CHO

HO y CHO OH

HO CHO

OH O

OH O

OH OH O

HO y CHO OH

OH OH OH O

OH OH OH O

OH OH OMe O

OH OH OMe O

Spinach

Spinach

Spinach

E. coli

Yeast E. coli

Yeast E. coli

Yeast

Spinach

Spinach

36-38

OH OH

Acceptor substrate

Product

Source

Ref.

"S OH

OH Me.A

OH OH

OH OH OH

"CHO

OH OH OH

"CHO

OMe O

O OH

OMe O

O OH

OH OH

OH OH OH O

LsAj^^OH

OH OH O

oh oh OH O

Spinach

Spinach

Spinach

Spinach

Yeast

Yeast E. coli

Yeast

Yeast Spinach

Spinach

Spinach

oh oh

Acceptor substrate

Product

Source

Ref.

OH OH

OH OH

OH OH

HO Y CHO

Oh oh OH OH

OH OH

OH OH O

OH OH

OH OH

OH OH OH O

OH OH OH O

OH OH OH O

OH OH O

OH OH O

OH OH O

Spinach

Yeast

Yeast

Yeast

Yeast

Yeast

Yeast

Yeast

Yeast Spinach

E. coli

E. coli

Yeast

OH OH OH

Acceptor substrate

Product

Source

Ref.

OH OH

^OH Qkcho

O^CHO

OH OH O

OH OH OH O

OH OH O

on^0H

Yeast

Yeast

Yeast

Yeast

Yeast E. coli

Yeast

Yeast

Yeast

E. coli

E. coli

glycolaldehyde, while the L-form exhibited zero and, accordingly, the L-isomer can be recovered after the incubation of racemic form with TKase and hydroxypyruvate. This protocol is indeed very good for the preparation of enantiomerically enriched forms of 2-hydroxy aldehydes with hydrophilic structure as summarized in Table 6. For this purpose, it is indispensable to provide hydroxylpyruvate, a rather expensive material, in large quantities. Elaborated procedures, such as amino acid oxidase-catalyzed preparation from D-serine48 and serine, as well as glyoxylate

Table 6

Kinetic resolution utilizing transketolase

Substrate

Recovery

Ref.

MeO.

PhCH2Ov^l_

PhCH2O

Me.A

Starting material

Intermediate

Target compound

Ref.

I^Y^CHO

OH O

OH OH O

OH OH O

S OH

HO OH H

S OH

OH OH O

Me^Ak

aminotransferase (SGAT)-catalyzed synthesis from L-serine and glyoxylic acid,47 have been reported.

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