Formation of Sulfur-Containing Carbohydrates

The limited stability of sulfur-containing carbohydrate derivatives renders their

isolation and identification rather difficult. (It must be borne in mind that the

reaction mechanisms presented in this chapter are based on investigations carried

out mainly during the period 1940–1960; no recent data are available to verify the

much-esteemed work of that period with more recent analytical approaches.)

Stable products from the reaction of sulfite with both reducing and nonreducing

[41]carbohydrate model compounds were obtained only with sulfite solutions

of higher pH (e.g., pH 6) [42]. Adler [43] crystallized a sulfonic acid derived

from glucose under the same pH.

Theander [44]showed the formation of such products to proceed in a similar

manner as shown for a xylose in Scheme 4.52. Sulfonic acid 66 was formed via

oxidation, and 65 by rearrangement of 4-sulfo-3-deoxy-glucosone 64, which in

turn was formed from the dicarbonyl intermediate 62 [45]. The formation of 64

from 63 was also shown to proceed [46].

4.3 Sulfite Chemical Pulping 421

HSO3

-

HO

HO

HOH2C

HO

OH

O

H

H

HO

HOH2C

O

OH

O

H

HOH2C

OH

OH

O

H

HOH2C

O

OH

O

H

HO3S

HOH2C O

OH

O

OH

HO3S

HOH2C

HO

OH

O

OH

HO3S

HSO3

-

38 62 63

Scheme 4.52 Possible mechanism of sulfonic acid formation from glucose [45].

In a later account, Yllner [47]studied the reaction of xylose with neutral sulfite

solution and isolated a,d-dihydroxy-c-sulfo-valeric acid. The reaction mechanism

proposed for the formation of this sulfo-sugar acid is similar to the peeling process

under alkaline conditions. Neutral sulfite systems seem to be “alkaline”

enough to promote the initial rearrangement and formation of the intermediate

3-deoxy-d- glycero -pentos-2-ulose, which reacts with the hydrogen sulfite at position

C4, a benzylic acid rearrangement (BAR) finally yields the stable acid (70) (cf.

Scheme 4.53).

HO

OH

O

H

OH

HO

HO

OH

OH

O

HO

O

OH

OH

HO OH

HO

HO

OH

O

H

H

HO

OH

O

H

O

HO3S

OH

O

OH

OH

HSO3

-

HO3S

OH

O

H

O

-H2O

BAR

A

69 70

B

Scheme 4.53 Possible formation of sulfonic acids from xylose

intermediates under neutral sulfite conditions.