Synthetic Methods for Carbohydrates

10

Preparation and Characterization of 1,6-Anhydro-3,4dideoxy-β-D-glycero-hex-3-enopyranos-2-ulose

Downloaded by UNIV OF SYDNEY on November 8, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0039.ch010

FRED SHAFIZADEH and PETER P. S. CHIN Wood Chemistry Laboratory, University of Montana, Missoula, Mont. 59801

Pyrolysis of carbohydrates results in transglycosylation (1,2), dehydration (3) and subsequent decomposition and charring reactions (4). These reactions offer some interesting products which can be used as intermediates for synthesis of carbohydrate derivatives. 1,6-Anhydro-3,4-dideoxy-β-D-glycero-hex-3-enopyranos-2-ulose (levoglucosenone) has recently teen detected in several labora tories (5-8) from the pyrolysis of cellulose containing an acidic catalyst and has been assigned the structures, namely 1,5-anhy dro-2,3-deoxy-β-D-pent-2-eno-furanose (a) and cis-4,5-epoxy-2pentenal (b) as well as the levoglucosenone structure (c) shown in Figure 1. The correct structure of this compound was con firmed in our laboratory by making crystalline derivatives (8), and by investigating the reaction of the isolated compound. These investigations revealed that levoglucosenone can be produced in comparable yields from the pyrolysis of various materials, such as acid-treated starch and waste papers, in addition to pure cellulose (Table I). These yields were deter mined by pyrolysis gas chromatography of small samples, using a pyrolysis temperature of 350°. The crude pyrolyzate contained, in addition to levoglucosenone, 2-furaldehyde as the major im purity. It was also found that levoglucosenone is unstable at high temperatures and could further pyrolyze, especially in the presence of zinc chloride (8). In previous studies, levoglucosenone was purified by pre parative gas chromatography, which was a time consuming method only suitable for small-scale preparation. In the current in vestigation, the following procedure was developed for a larger scale preparation. Waste Kraft paper bags were shredded, treated with dilute phosphoric acid and dried. Eight-gram batches of the treated paper containing 5% phosphoric acid were pyrolyzed under nitrogen in a tube furnace. To minimize the ex cessive decomposition of the products on the hot furnace tube, a reduced temperature of 275° was used. After 208 g of the raw material was pyrolyzed, the accumulated pyrolyzate was extracted 179

El Khadem; Synthetic Methods for Carbohydrates ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

180

SYNTHETIC METHODS

FOR CARBOHYDRATES


H

Figure 1. Structures of (a) l,5-anhydro-2,3-deoxy-fi-O-pent-2-enofuranose; (b) cis4,5-epoxy-2-pentenal; and (c) l 6-anhydro-3 4-diaeoxy^-O-glycero-hex-3-enopyranos-2-ulose (levoglucosenone) }

TABLE I.

f

YIELDS OF LEVOGLUCOSENONE FROM THE PYROLYSIS OF DIF FERENT MATERIALS AT 3 5 0 . o a

Material

Neat

(%)

5% H P 0 - t r e a t e d 3

4

Cellulose

1.2

11.1

Starch

0.3

9.0

T*

9.1

News-print with

ink

K r a f t shopping bags

Determined by p y r o l y z i n g the v o l a t i l e s by GLC.

Τ

(%)

10.2

5 mg samples and d i r e c t l y

analyzing

Τ = t r a c e amount.



10.

S H A F i z A D E H AND CHIN

Preparation

of

181

Levoglucosenone

with chloroforrn and the chloroform solution was dried, filtered and evaporated. The gas-liquid chromatography (GLC) analysis of this mixture gave chromatogram A in Figure 2, showing the levo glucosenone and 2-furaldehyde as the major components with the ratio of 4:1, respectively. 2-Furaldehyde and other aldehydo impurities were removed from the pyrolyzate by reaction with 5,5-dimethyl-l,3-cyclohexane-dione (dimethone) in 50% aqueous ethanol solution at 100°. Upon cooling, the bismethone derivatives of aldehydo compounds precipitated from the solution and were removed by f i l tration. Ethanol was removed from the filtrate under vacuum and the remaining aqueous solution was again extracted with chloro form, dried, filtered, and evaporated. The resulting mixture gave chromatogram Β in Figure 2, which shows the complete re moval of 2-furaldehyde along with other aldehydo impurities. This aldehyde-free pyrolyzate was then vacuum distilled at 1.5 mm Hg. The fraction collected between 55-60° as shown in chroma togram C in Figure 2, contained 96% levoglucosenone, pure enough for synthetic purposes. The yield of purified product weighed 6.8 g, amounting to an overall yield of 3.3% based on the weight of waste paper. 26 The product was a light-yellow colored liquid with [a] 458°, compared with the -460° reported before (7). This product was further characterized as the crystalline 2,4-dinitrophenylhydrazone (DNPH) reported before (8) and semicarbazone which is a new derivative. Levoglucosenone possesses an interesting α,3-unsaturated keto structure, which can be used to synthesize branched-chain, keto and amino sugar derivatives. In this study, we have ex plored some of these possibilities. Table II shows some of the derivatives prepared by modifying the functional groups of this compound. Selective reduction of the keto group by lithium aluminum hydride in ether gave a mixture containing 84% of 1,6-anhydroD

3,4-dideo^-e-D-erythro-hex-3-enopyranose (d) and 8% of its C-2

epimer. The major product formed in 75% yield, and was charac terized by i t s 3,5-dinitrobenzoate derivative. The nuclear mag netic resonance (NMR) spectrum of this compound showed that there was no spin-spin coupling between the CI and C2 protons, con firming the assigned configuration. The second derivative was prepared by hydrogénation of the double bond using Pd/BaSÛ4 as a catalyst. This gave 1,6-anhydro3,4-dideoxy-6-D-giycero-hexopyranos-2-ulose (e) as an oil in 85% yield. This compound was characterized by i€s DNPH derivative. The reduction of both keto and double bond functional groups gave 1,6-anhydro-3,4-dideoxy-3-D-erythro-hexopyranose (f) as an o i l , that was characterized by I t s 3,5-dinitrobenzoate derivative. The same product-, 3,5-dinitrobenzoate derivative, was obtained by both hydrogénation of d or reduction of e; indicating that the saturation of the double bond on the sugar ring did not change


182

M E T H O D S FOR CARBOHYDRATES


SYNTHETIC

c

Figure 2. Gas-liquid chromatograms of (A) crude prolyzate; (B) crude pyrolyzate after removing aldehydo impurities; and (C) final product. Peak a is 2-furaldehyde and peak b is levoglucosenone.

50

82

114

146

178

2li>

ISOTHERMAL



(s)

• ο «

•o

OH

(SÎ

(£)

-o

Ether

LiAlH, 4

Pd/BaSO,

Pd/BaSO,

Ether

L i AT Hy,

(i)

(1)

(·)

(i)

OH

•o

70

84

85

75

Yield

{%) by

3,5-DNB derivative

derivative

3,5-DNB

derivative

DNPH

derivative

3,5-DNB

Characterized

Note

DERIVATIVES OF LEVOGLUCOSENONE PREPARED BY MODIFYING ITS FUNCTIONAL GROUPS.

Reaction & Product

TABLE II.



184

SYNTHETIC METHODS

FOR CARBOHYDRATES

the stereospecific nature of the lithium aluminum hydride reaction and also confirming the assigned configuration. The former reaction gave 84% yield and the latter reaction gave 70% yield of the major product and 7% of the corresponding isomer. In addition to modifying the functional groups of levoglucosenone, different branched-chain sugar derivatives could also be prepared by the reaction of levoglucosenone with Grignard reagent under controlled conditions as shown in Table I I I . At room temperature, levoglucosenone reacted with methylmagnesium iodide to give mainly the 1,2 addition product, 1,6anhydro-3,4-dideo)^"2-c-methyl^-p-erythro-hex-3-enopyranose (g) in 56% yield. The reaction mixture also contained 6% of the C-2 epimer and 6% of the 1,4-addition product. The major product was separated by column chromatography (CC), reduced by hydrogénation to 1,6-anhydro-3,4-dideoxy-2-c-methyl -3 -D-erythro-hexopyranose (h), and characterized as the 3,5-dinitrobenzoate derivative. At -78° and in the presence of tetrakis [iodo (tri-n-butylphosphine) copper (I)], however, the reaction of levoglucosenone with methyl magnesium iodide gave mainly the 1,4-addition product, 1,6-anhydro-3,4-dideoxy-4-c-methyl-6 -D-erythro-hexopyranos-2ulose, (i) in 64% yield. This compound was characterized as the DNPH derivative. The configuration of compound 2 was assigned by ΝMR spectroscopy which showed that there was no spin-spin coupling between the C4 and C5 protons. The reaction of e with methylmagnesium iodide at room temp erature was not stereospecific. It gave nearly equal amounts of compound h and 1,6-anhydro-3,4-dideoxy-2-c-methyl-β-J-threohexopyranose"(j) as an o i l which could not be clearly separated by CC. However, these two compounds were characterized by their 3,5-dinitrobenzoate derivatives from the early and late fractions. The configurations of compounds g,h and j were determined by NMR spectroscopy with the aid of europium III [Eu (fod)o] shift reagent. The NMR of the product mixture containing h and j in CDClj shown in spectrum A in Figure 3, contains two equal sized hydroxyl signals at 2.5 and 2.8 ppm due to the equal con centrations of the two compounds. There was only one sharp signal at 5 ppm for the anomeric protons. In order to increase the concentration of one of the two isomers, compound g was hydrogenated to h and added to the solution. This increased the size of the hydroxy! signal at 2.5 ppm as shown in spectrum Β in Figure 3. Upon gradual addition of Eu (fod)3, as shown in spectra C and D, the larger hydroxyl signal at 2.5 ppm shifted significantly to a lower field while the other one remained re latively unchanged. Also, the common signal for the anomeric protons at 5 ppm was gradually separated into two peaks. The peak which shifted to a lower field was larger in size than the one remaining relatively unchanged. Therefore, the isomer pre pared by hydrogénation of compound g should have the structure h that contains the more accessible~hydroxyl group.



;°,

(·)

(£)

(£)

(

-78°

Room Temp.

3

CH MgI

3

n-Bu PCuI

3

CH MgI

Room Temp.

CH~MgI

->

(J)CHl

(fe)

M

\ *

(i)

(s)

31

31

64

56

Yield GLC Analysis

[%)

44

51

Isolated

3,5-DNB derivative

3,5-DNB derivative

DNPH derivative

Characterized

by

J

4,5

Note

0 cps

DERIVATIVES OF LEVOGLUCOSENONE PREPARED BY GRIGNARD REACTIONS UNDER DIFFERENT CONDITIONS.

Reaction & Product

TABLE III.



186

SYNTHETIC METHODS FOR CARBOHYDRATES

J 6

5

1

4

1

•

8

2

'

1

OPPM

'

6

'

5

'

4

I

8

I

2

I

1

0 PPM

Figure 3. Gradual change in nmr spectra; (A) Grignard reaction products of compound e; (B) after adding the hydrogénation product of compound e; (C) after adding Eu(fod) ; and (D)at the end of the addition of Eu(fod) s

s


10. SHAFIZADEH AND CHIN

Preparation of Levoglucosenone

187


Literature Cited 1. Shafizadeh, F., Adv. Carbohyd. Chem., (1968), 23, 419-474. 2. Shafizadeh, F. and Fu, Y. L., Carbohyd. Res., (1973), 29, 113-122. 3. Shafizadeh, F. and Lai, Y. Z.,Carbohyd.Res., (1975), 40, 263-274. 4. Lai, Y. Z. and Shafizadeh, F.,Carbohyd.Res.,(1974), 38, 177-187. 5. Lipska, A. E. and McCasland, G. E., J. Appl. Polym. Sci., (1971), 15, 419-435. 6. Lam, L. Κ. Μ., Fung, D. P. C., Tsuchiya, Y., and Sumi, K., J. Appl. Polym. Sci., (1973), 17, 391-399. 7. Halpern, Y., Riffer, R., and Broido, Α.,J.Org.Chem., (1973), 38, 204-209. 8. Shafizadeh, F. and Chin, P. P. S., Carbohyd. Res., (1976), 46, 149-154.


Synthetic Methods for Carbohydrates

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