Enzymatic Selective Transformations of Diethyl Fumarate

Tetrahedron

Vol. 51. No. 28. DD. 77157720. 1995 Copyright Q 1995 ‘Ejsevier Scieks Ltd Printed in Great Britain. All rights reserved OCMO-4020/95 $9.50+0.00

0040-4020(95)0039

Enzymatic

Selective

l-6

Transformations

of

Diethyl

Fumarate

Margarita Quir6s, Covadonga Astorga, Francisca Rebolledo and Vicente Gotor* Depariamen~o

Abstrad: solvents. enzymatic contrast.

de Qufmica Orghnica e InorgAnica

Universidad

de Oviedo. 33071 Oviedo. Spain.

Candida antarctica lipase selectively catalyses transformations of diethylfumarate in organic A range of nitrogen nucleophiles, including ammonia, can be succesfully used in these reactions, monoamides and monohydrazides being obtained in high to moderate yields. In diethyl maleate is not an adequate substrate for his enqme.

INTRODUCTION Selective transformation of only one function of a di- or polyfunctionalized molecule is always an operation of synthetic utility in organic chemistry. Owing to the selective properties of the enzymes, these biocatalysts, especially lipases, have been extensively employed to carry out biotransformations

of diesters,l

diols,a carbohydrates,3 or nucleosides,a mainly through hydrolysis, esteriflcation and transesterification reactions. Although lipase catalyzed aminolysis has been less studied, we have demonstrated its usefulness in order to obtain selectively monoamidation

compounds from saturated diesters and aliphatic amines or diamines.6

In addition, the great catalytic efficacy of the lipases allows the preparation,

in mild conditions, of certain a$-

unsaturated amides’ and hydrazides ,s which are difficult to obtain directly from the corresponding

ester and

amine or hydrazine because of the competitive Michael-type addition, Taking into account the aforementioned properties of lipases, we envisioned that it couId be of interest to study the enzymatic reactions of a&unsaturated diesters such as diethyl fumarate and maleate with nitrogen nucleophiles as amines, ammonia and hydrazines; especially, if one consideres that the conventional preparation of monoamides or monohydrazides derived from the above a&unsaturated diesters requires several steps. For example, the preparation of some monoamides derived from the fumaric ester is carried out by treatment of the fumaric acid monoalkyl ester with oxalyl chloride, and further reaction with the appropriate amine.9 On the other hand, the isomeric substrates that we have chosen allow us to study the influence of the P system geometry in the catalytic activity of the biocatalyst, an important matter due to the well-documented fact that the presence of unsaturations in the substrates, as well as their double bond configuration, dramatically affect the activity of some lipases.10 7715

7716

M. QUIRKS

RESULTS

et al.

AND

DISCUSSION

We start the study on the aminolysis of a,&unsaturated diesters using Candida antarctica lipase (CAL) as catalyst, because this enzyme has displayed a great efficacy in other aminolysis processes.s.s,tl The aminolysis of diethyl fumarate (1) with butylamine (3a), in dioxane as solvent and CAL as catalyst, takes place smoothly, and the monoamidation compound Sa is obtained as the sole product (see scheme 1). However, under the same reaction conditions, but in the absence of enzyme, a high percentage of the corresponding Michael adduct (4a) is obtained. When the enzymatic aminolysis is applied to diethyl maleate (2), the obtained a$unsaturated amidoester is identical with that isolated in the reaction of diethyl fumarate, that is, with frunsgeometry. The formation of this compound probably takes place via a previous Michael/retro-Michael-type isomerisation of diethyl maleate to fumarate, followed by the lipase-catalysed aminolysis of fumarate. As a proof of the above isomerisation, the 24 h-reaction of diethyl maleate (2) with butylamine in the absence of enzyme leads to a mixture of 1 and the Michael adduct 4a (see scheme 1). These results suggest that either butylaminecatalysed isomerisation of diethyl maleate is faster than its lipase-catalysed aminolysis, or diethyl fumarate is a considerably better substrate than diethyl maleate for the lipase. We have also tried the enzymatic reactions of diethyl fumarate (1) and maleate (2) with other nitrogen nucleophiles such as isopropylamine, 2-aminoethanol, ammonia and diamines. In all the cases, the transmonoamidoesters 5 are the only isolated products, and the yields are significantly higher starting from 1 than when 2 is the substrate (see table). Although with diamines the acylation of both amino groups takes place (compounds 5e and 5f), with 2-aminoethanol the enzyme is selective towards the amino group, no product corresponding to the acylation of the primary hydroxyl group is detected. In the absence of enzyme, mixtures of 1 and 4 are obtained with both diesters, except in the reactions of 2 with ammonia (3d) and hexane- 1,6diamine (3f), for which mixtures of 1,2 and 4 are reached. The presence of 2 in these mixtures means that its isomerization is slower than with the other nucleophiles; consequently, and taking into account the results of the corresponding enzymatic reactions, it is evident that the lipase shows a higher catalytic activity with diester 1 than with diester 2, presumably because compound 1 is better fitted than compound 2 into the active site of the enzyme. Scheme 1 0

NHR

5e-f

Sa-d I 3a-f a, R = Bu; b, R = pi; c, R = CHzCH20H;

*

1

+

(2)

+

4a-f

d, R = H, e, R = (CH2)2NH2; f, R = (CH&NH2

Diethyl fumarate

Table. Aminolysis

and Ammonolysis

Ester

Product

Reaction time, h

1

5a

24

2

5a

1

7717

Reactions Catalyzed by CAL

Yield? %

Reaction time, h

Yield:

Ester

Product

62

1

5d

66

35

24

54

2

Sd

66

15

Sb

98

40

1

5e

42

74

2

Sb

98

32

2

5e

42

48

1

SC

40

96

1

5f

72

69

2

5C

40

61

2

5f

96

29

%

a Calculated after column chromatography purification. In addition, we have studied the reaction of these a&unsaturated

esters (1 and 2) with acetylhydrazine

(6). In the presence of lipase, diethyl fumarate (1) reacts with 6, the corresponding hydrazide 7 being obtained as the sole compound (95% yield, 3 days, r.t.). However, in the same reaction time, the lipase does not catalyse the hydraziiolysis of diethyl maleate (2). Only after 7 days, a 70: lo:20 mixture of diethyl maleate (2), truns- (7) and cis-hydrazide (8) is observed in the crude (scheme 2). The small amount of 7 is probably a consequence of the slow isomerisation of diethyl maleate to fumarate in the presence of 6. Moreover, the low percentage of cishydrazide 8, as compared with the high one of the unreacted substrate, is another sign of the low catalytic activity of the Candida antarctica lipase toward diethyl maleate. Scheme

2 0

2

+

Me

ji

N’ H

NH2

NH-NHCOMe

=+ 30%

0

conv.

m

/

+

NlSNHCOMe OEt

1 c

0

6

0 7

8

Although the last reaction is significant proof of the different activity of Can&a antarctica lipase with diethyl fumarate and maleate, we believe it is of interest to try other enzymatic transformations with other lessbasic nucleophiles such as water and butan-l-01. These reagents do not promote the isomerisation of 2 in the current reaction conditions. The hydrolysis and transesterification of diethyl fumarate in dioxane are noticeably slower than the aminolysis and hydrazinolysis, leading after 6 days to the corresponding monoacid (9) and a mixture of monobutyl (10) and dibutyl esters (11) in a 73:27 ratio12 (see scheme 3). However, no transformation of diethyl maleate is observed in the same reaction conditions. This great difference of activity of the CAL towards diethyl maleate is in agreement with the activity exhibited by other enzymes, such as porcine pancreatic, Candida cylindracea, Mucor miehei and Pseudomonas fluorescens lipases, which catalyse the polytransesterification

of fumaric esters with butan-1,4diol,

but do not accept maleate esters as substrates.lM

7718

M.

QUIRKS

et al.

Scheme 3

In summary, we have developed a very mild and simple method to carry out selective transformations of diethyl flJmarate, being of especial importance for the preparation of monoamides and monohydrazides. Moreover, we have demonstrated that its isomer, diethyl maleate, is not a substrate for the CAL, which can be of great utility for further design of empiric models of the active site of this enzyme.

EXPERIMENTAL

SECTION

General. Candida antarctica lipase, SP 435, was given by Novo Nordisk Co. All reagents are purchased from Aldrich Chemie. Solvents are distilled over an adequate desiccant and stored under nitrogen. For column chromatography, Merck silica gel 60/230-400 mesh is used. Mp’s are taken using a Gallenkamp apparatus and are uncorrected. IR spectra are recorded on a Perkin-Elmer 1720-X FT Infrared spectrophotometer. iH- and W-NMR spectra are obtained using a Bruker AC-300 (rH- 300 MHz and W- 75.5 MHz) spectrometer. Mass spectra are recorded on a Hewlett-Packard 5987 A spectrometer. Microanalyses are performed on a Perkin-Elmer

240B elemental analyser, and are satisfactory for all compounds.

General procedure for the synthesis of amidoesters 5a-c and bis(amidoesteres) 5e-f. 2.5 mm01 of diester (for 5a-c) or 5 mmol (for 5e-f) and 2.5 mmol of amine or diamine are added to a suspension of CA lipase (150 mg) in dioxane (20 ml) under nitrogen atmosphere. The mixture is shaken at 30°C and 250 rpm during the time indicated in the table. The enzyme is then filtered, washed with dichloromethane, and organic solvents are evaporated. The residue is subjected to column chromatography using as eluents: ethyl acetate-hexane 1: 1 for 5a,b; ethyl acetate for SC; and acetonitrileether-isopropyl Ethyl

(E)-3-(N-bufylcarbamoyl)prop-2-enoate

alcohol 10: 10:0.2 for 5e-f.

(Sa): M.p. 63-64 “C; IR (KBr)

cm-i; tH NMR (CDC13) 6 @pm): 0.93 (t, 3H, CHs), 1.32 (t, 3H,

CH3),

1.39

1717, 1667

(m, 2H, CH2), 1.55 (m, 2H,

CH2), 3.37 (m, 2H, CHzN), 4.24 (q, 2H, CH20), 6.32 (bs, lH, NH), 6.83-6.96 (ABq, 2H, =CH, J = 15.5); tsC NMR (CDC13) 6 (ppm): 13.6 (CHs), 14.0 (CH3), 20.0 (CH2), 31.3 (CH2). 39.6 (CH&

61.1 (CH2),

130.0 (CH), 136.6 (CH), 163.6 (C=O), 165.7 (C=G); MS (70 eV) m/z 199 (M+, 3 “/OX 127 (100). Anal. Calcd. for CtoHt7N03: C, 60.27; H, 8.60; N, 7.03. Found: C, 60.19; H, 8.70; N, 7.11. Ethyl (E)-3-(N-isopropylcarbamoylrop-2-enoate (5b): M.p. 84-86’C; IR (KBr) 1637, 1725 cd; 1H NMR (CDCls) 6 (ppm): 1.21 (d, 6H, CHs), 1.31 (t, 3H, CHs), 4.18 (m, lH, CH), 4.24 (q, 2H, (ABq, 2H, =CH, J = 15.5); 13C NMR (CDCls) 6 (ppm): 14.0 (CH3). 22.4 (2CHs), 41.8 (CH), 61.1 (CH3), 129.9 (CH), 136.8 (CH), 162.6 (C=O), 165.7 (C=O); MS (70 eV) m/z CH20).

6.23 (bs, lH, NH), 6.82-6.94

7719

Diethyl fumarate

185 (M+, 6 %), 127 (100). Anal. Calcd. for CsHt5NOs

: C, 58.35; H, 8.17; N, 7.57. Found: C, 58.46; H,

8.26; N, 7.48. Ethyl

(E)-3-[N-(2-hydroryethyl)carbamoyl]prop-2-enoute

(5~): oil; IR (KBr)

1723, 1670

cm-l; 1H NMR (CDCls) S (ppm): 1.32 (t, 3H, CHs), 3.53 (m, 2H, CHzN), 3.78 (t, 2H, CHzO), 4.25 (q, 2H, CH20), 6.83-6.98

(ABq, 2H, =CH, J = 15.6); W NMR (CDCls) S @pm): 14.0 (CHs), 42.4

(CH2), 61.2 (CH2), 130.1 (CH), 136.3 (CH), 164.6 (GO), 127 (100). Anal. Calcd. for CsHtsNO4

165.8 (C=O); MS (70 eV) m/z 187 (M+, ~1 %),

: C, 51.31; H, 7.00; N, 7.48. Found: C, 51.41; H, 7.08; N, 7.39.

Ethyl (E)-3-(carbamoyl)prop-2-enoute

(Sd): The procedure

is similar

using a 2% solution of ammonia in dioxane. M.p. 93-95°C; IR (KBr) 1708, 1685 @pm):

1.25

(CHz), 61.0

as described cm-l;

II-l

3H, CHs), 4.18 (q, 2H, CH2), 6.20 (bs, lH, NH), 6.36 (bs, lH, NH), 6.75-6.93

0,

for 5a but

Nh4R

(CDCl,)

6

(ABq, 2H,

=CH, J = 15.5); rsC NMR (CDCls) S @pm): 14.0 (CHs), 61.3 (CH2). 131.3 (CH), 135.5 (CH), 165.4 (GO), 165.8 (GO);

MS (70 eV) m/z 143 (M+, 3 %), 98 (100). Anal. Calcd. for C6H9Nos:

C, 50.33; H, 6.34; N,

9.79. Found: C, 50.42; H, 6.25; N, 9.71. Diethyl (2E,ZOE)-4,9-dioxo-5,8-diuzudodecu-2,ZO-dienedioute (Se): M.p. 189-190°C, IR (KBr) 1631, 1713 cm-r; tH NMR (CDCls) S (ppm): 1.32 (t, 6H, CH3), 3.54-3.59 (m, 4H, CH2NH), 4.25 (q, 4H,

6.81-6.93

4H, =CH, J = 15.4), 7.26 (bs, 2H, NH); 13C NMR (CDC13) S (ppm): 14.1 (CH3), 40.2 (CH2). 61.3 (CH2). 130.8 (=CH), 135.7 (=CH), 165.0 (C=O), 165.4 (C=O); MS (70 eV) m/z 312 OCH2),

(ABq,

@I+, ~1%)~ 128 (100). Anal

Calcd. for Cr4H~oN20,j

: C, 53.84; H, 6.45; N, 8.97. Found: C, 53.91; H, 6.32;

N. 9.08. Diethyl “C; IR (nujol)

(2E,Z4E)-4,13-dioxo-5,22-diazuhexudecu-2,24-dienedioate

1628, 1712 cm-t; 1H NMR @MSO-d6)

(5f): M.p.

181-182

S @pm): 1.23 (t. 6H, CHs), 1.24-1.30 (m, 4H, CH2),

1.31-1.50 (m. 4H, CH2), 3.14 (q. 4H, CHzNH), 4.17 (q, 4H, OCHz), 6.66-6.88 8.52 (t, 2H, NH); W NMR (CDC13) S (ppm): 14.1 (CHs), 25.5 (CH&

(ABq, 4H, =CH, J = 15.2),

29.1 (CH2). 39.1 (CHz), 61.2 (CHz),

130.4 (=CH), 136.2 (=CH), 163.8 (C=O), 165.6 (C=O) ; MS (70 eV) m/z 368 ( M+, cl%), 98 (100). Anal. Calcd. for CtsH2sN206

: C, 58.68; H, 7.66; N, 7.60. Found: C, 58.76; H, 7.57; N, 7.52.

Ethyl (2E)-4,7-dioxo-5,6-diuzuocta-2-enoate (7): 5 mm01 (0.81 ml) of diethyl fumarate and 5 mm01 (0.37g) of acetylhydrazine are added to a suspension of CA lipase (300 mg) in dioxane (30 ml) under nitrogen atmosphere. The mixture is shaken at 30°C and 250 rpm during 72h. Afterwards, the procedure is the same as described for 5e-f. M.p. 225-227°C;

IR (nujol)

1582, 1605, 1723 cm-r; rH NMR (CDsOD) S @pm):

1.50 (t, 3H, CHs), 2.21 (s, 3H, CH3), 4.44 (q. 2H, CH2), 7.01-7.03 (ABq, 2H, =CH, J = 15.7); t3C NMR (CDsOD) S (ppm): 14.9 (CHs), 20.9 (CHs), 62.9 (CH2), 132.8 (=CH),

135.4 (=CH),

165.1 (C=O),

(C=O), 172.1 (C=O); MS (70 eV) m/z 200( M+, 8%), 127 (100). Anal. Calcd. for CsHr2N204 6.04; N, 13.99. Found: C, 48.07; H, 6.12; N, 13.88.

167.1

: C, 47.99; H,

7720

M. QUIFXIS et al.

(E)-3-Ethoxycarbonylprop-2-enoic acid (9). The procedure is similar as described for 5a-c, but the residue is recrystallised in chloroform-hexane. Yield, 78%; m.p. 66-68’C, identical to a sample purchased from Aldrich Chemie. tH NMR (CDC13) 6 (ppm): 1.34 (t. 3H, CH3), 4.28 (q, 2H, CHp), 6.80-6.98 (ABq, 2H, =CH, J = 15.7), 9.29 (bs, lH, OH); t3C NMR (CDQ) (CW, 164.6 (C=O), 170.0 (GO);

S @pm): 14.0 (CHs), 61.5 (CH&

132.6 (CH), 135.6

MS (70 eV) m/z 99 (100). ACKNOWLEDGEMENTS

We are grateful to the Comisi6n Interministerial de Ciencia y Tecnologfa (Proyecto BIO 92-0751), and to NOVO Nodisk Co. for the generous gift of the CA lipase. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

11. 12.

AND

NOTES

a) Toone, E. J.; Werth, M. J.; Jones, J. B. J. Am. Chem. Sot., 1990, 112, 4946. b) Gutman, A. L.; Shapira, M. J. Chem. Sot., Chem. Commun., 1991, 1467. Ferraboschi, P.; Casati, S.; Grisenti, P.; Santaniello, E. Tetrahedron: Asymmetry, 1994,5, 1921. Pulido, R.; Gotor, V. Carbohydr. Res., 1994, 252, 55. Moris, F.; Gotor, V. J. Org. Chem., 1993,58, 653. Puertas, S.; Rebolledo, F.; Gotor, V. Tetrahedron, 1995,5I, 1495. Astorga, C.; Rebolledo, F.; Gotor, V. J. Chem. Sot. Perkin Trans. I, 1994, 829. Puertas, S.; Brieva, R.; Rebolledo, F.; Gotor, V. Tetrahedron, 1993,49,4007. Astorga, C.; Rebolledo, F.; Gotor, V. Synthesis, 1991, 350. Home, S.; Taylor, N.; Collins, S.; Rodrigo, R. J. Chem. Sot. Perkin Trans. I, 1991, 3047. a) Guanti, G.; Narisano, E.; Podgorski, T.; Thea, S.; Williams, A. Tetrahedron:, 1990,46, 7081. b) Guanti, G.; Banfi, L.; Narisano, E. Tetrahedron: Asymmetry 1990, I, 721. c) Haraldsson, G. G.; Gudmundsson, B. 6.; Almarsson, 6 Tetrahedron Lett., 1993,34, 5791. d) Geresh, S.; Gilboa, Y. Biotechnology and Bioengineering, 1990,36,270. a) Garcia, M. J.; Rebolledo, F.; Gotor, V. Tetrahedron: Asymmetry, 1993,4, 2199. b) Garcia, M. J.; Rebolledo, F.; Gotor, V. Tetrahedron, 1994.50, 6935. The ratio of compounds 10 and 11, as well as their characterizations are accomplished by GC-MS; the mixture is not resolved.

(Received in UK 23 February 1995; revised 17 May 1995; accepted 19 May 1995)