Synthesis of a maradolipid without using protecting groups

Article abstract of DOI:10.1016/j.tetlet.2013.02.076

A convenient route has been developed to synthesize 6-O-mono- and 6,6′-di-O-acyl symmetrical and unsymmetrical (un)-symmetrically trehalose derivatives from trehalose using a combination of enzymic and nonenzymic reactions. Thus, a typical maradolipid was accessed in two-steps.

Full text of DOI:10.1016/j.tetlet.2013.02.076

Tetrahedron Letters 54 (2013) 2274–2276
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Tetrahedron Letters
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Synthesis of a maradolipid without using protecting groups
⇑
René Csuk , Andrea Schultheiß, Sven Sommerwerk, Ralph Kluge
Martin-Luther-Universität Halle-Wittenberg, Organische Chemie, Kurt-Mothes-Str. 2, D-06120 Halle, Saale, Germany
a r t i c l e i n f o
a b s t r a c t
A convenient route has been developed to synthesize 6-O-mono- and 6,60-di-O-acyl symmetrical and
unsymmetrical (un)-symmetrically trehalose derivatives from trehalose using a combination of enzymic
and nonenzymic reactions. Thus, a typical maradolipid was accessed in two-steps.
Ó 2013 Elsevier Ltd. All rights reserved.
Article history:
Received 20 January 2013
Revised 21 February 2013
Accepted 22 February 2013
Available online 1 March 2013
Keywords:
Maradolipid
Chemoenzymatic trans-esterification
Trehalose
Introduction
for the straightforward synthesis of complex (un)-symmetrically
substituted maradolipids remained unexploited.
Primary mono- and diesters of
a
,
a
-trehalose (1, Fig. 1) are
Thus, the reaction of trehalose dihydrate (1, Scheme 1) with
vinyl oleate (3) in the presence of Novozyme 43516,17 for 2 days
gave quite nicely the 6,60-di-O-oleoyl-derivative 5; under the same
conditions from 1 and 418 6,60-di-O-13-methylmyristoyltrehalose 6
was obtained. Attempts to use this enzyme to obtain 6-O-mono-
important components1–3 of the outer membrane of mycobacteria,
and they have been isolated from the enduring larvae of the nem-
atode Caenorhabdis elegans helping this organism to survive condi-
tions of extreme desiccation.4,5 One of the most abundant
components is an unsymmetric 6,60-trehalose diester, 6-O-(13-
methylmyristoyl)-6’-O-oleoyltrehalose (2),5 and several routes
have been devised to access this class of interesting compounds,
also known as maradolipids.
acylated compounds
7 and 8 failed to give good yields.
Reproducibly high yields of 7 and 8 were obtained, however, by
using the commercially available enzyme Alcalase from Bacillus
licheniformis.19
By and large different protecting groups have been used includ-
ing the temporary protection of the hydroxyl groups with silyl or
trityl groups or by converting the primary hydroxyl groups into
halides or sulfonates before carrying out SN2 reactions employing
carboxylate salts.2,6–11
The reaction of 1 with a 1:1 mixture of the vinyl esters 3 and 4
in the presence of Novozyme 435 gave a mixture of mono-
acylated products 7 and 8 together with an unseparable mixture
Recently, an elegant approach utilizing a primary selective desi-
lylation12 of persilylated trehalose has been reported by Knölker
et al.13
Protecting-group-free strategies appear to be most elegant.
Thus, in Grindley’s recent approach, an uronium-based coupling
reagent has been used14 allowing the two-step synthesis of marad-
olipids without protecting groups in good yields.
Results and discussion
The selective chemoenzymatic monoesterification of mono- and
disaccharides has been known for a long time. Thus, the monoeste-
rification of the primary hydroxyl group of 1 has been described a
decade ago15 but the potential of these enzymic transformations
⇑
Corresponding author. Tel.: +49 (0) 345 5525660; fax: +49 (0) 345 5527030.
E-mail address: rene.csuk@chemie.uni-halle.de (R. Csuk).
Figure 1. Structure of trehalose (1) and maradolipid (2).
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.02.076

R. Csuk et al. / Tetrahedron Letters 54 (2013) 2274–2276
2275
Scheme 1. Synthesis of mono- and sym. diacylated trehalose derivatives as well as of maradolipid 2.
of diacylated 2, 5, and 6. In addition, the Novozyme 435 or
References and notes
alcalase catalyzed acylations of 7 and 8 proceeded very slowly,
and it was not possible to isolate significant amounts of
maradolipid 2.20 As an alternative, monoacylated 7 and 8 were
subjected to Mitsunobu reactions in hexamethylphosphorous
triamide (HMPTA)21 to yield the unsymmetrically substituted
maradolipid 222 in 69–71% yields.
1. Noll, H.; Bloch, H.; Asselineau, J.; Lederer, E. Biochim. Biophys. Acta 1956, 20,
299–309.
2. Khan, A. A.; Chee, S. H.; McLaughlin, R. J.; Harper, J. L.; Kamena, F.; Timmer, M.
S. M.; Stocker, B. L. Chembiochem 2011, 12, 2572–2576.
3. Hutacharoen, P.; Ruchirawat, S.; Boonyarattanakalin, S. J. Carbohydr. Chem.
2011, 30, 415–437.
4. Erkut, C.; Penkov, S.; Khesbak, H.; Vorkel, D.; Verbavatz, J. M.; Fahmy, K.;
Kurzchalia, T. V. Curr. Biol. 2011, 21, 1331–1336.
5. Penkov, S.; Mende, F.; Zagoriy, V.; Erkut, C.; Martin, R.; Pässler, U.; Schuhmann,
K.; Schwudke, D.; Gruner, M.; Mantler, J.; Reichert-Muller, T.; Shevchenko, A.;
Knölker, H.-J.; Kurzchalia, T. V. Angew. Chem., Int. Ed. 2010, 49, 9430–9435.
6. Lederer, E. Chem. Phys. Lipids 1976, 16, 91–106.
7. Barry, C. S.; Backus, K. M.; Barry, C. E.; Davis, B. G. J. Am. Chem. Soc. 2011, 133,
13232–13235.
8. Sanki, A. K.; Boucau, J.; Umesiri, F. E.; Ronning, D. R.; Sucheck, S. J. Mol. Biosyst.
2009, 5, 945–956.
9. Nishizawa, M.; Garcia, D. M.; Minagawa, R.; Noguchi, Y.; Imagawa, H.; Yamada,
H.; Watanabe, R.; Yoo, Y. C.; Azuma, I. Synlett 1996, 452–454.
10. Nishizawa, M.; Yamamoto, H.; Imagawa, H.; Barbier-Chassefiere, V.; Petit, E.;
Azuma, I.; Papy-Garcia, D. J. Org. Chem. 2007, 72, 1627–1633.
11. Sarpe, V. A.; Kulkarni, S. S. J. Org. Chem. 2011, 76, 6866–6870.
12. Toubiana, R.; Das, B. C.; Defaye, J.; Mompon, B.; Toubiana, M. J. Carbohydr. Res.
1975, 44, 363–369.
In summary, symmetrical 6,60-di-O-acylated trehalose deriva-
tives can be accessed from trehalose by using the enzyme Novo-
zyme 435 in transesterification reactions employing the
corresponding vinyl carboxylates whereas the corresponding
monoesters can be obtained using the Alcalase from B.
licheniformis.
Unsymmetrically substituted diesters can be obtained by a two-
step procedure of a chemoenzymatic monoacylation followed by a
regioselective monoacylation either by a Mitsunobu reaction21 as
here, or using uronium-based promotion of esterification.14 Thus,
maradolipid 2 was obtained in an over-all yield of approx. 50% in
a two-step sequence.
13. Pässler, U.; Gruner, M.; Penkov, S.; Kurzchalia, T. V.; Knölker, H.-J. Synlett 2011,
2482–2486.
Acknowledgment
14. Paul, N. K.; Twibanire, J.-D. A.; Grindley, T. B. J. Org. Chem. 2013, 78, 363–369.
15. Raku, T.; Kitagawa, M.; Shimakawa, H.; Tokiwa, Y. J. Biotechnol. 2003, 100, 203–
208.
16. Liu, J.; Park, S. K.; Moore, J. A.; Cramer, S. M. Ind. Eng. Chem. Res. 2006, 45, 9107–
9114.
We like to thank Dr. D. Ströhl for measuring the NMR spectra
and Mrs. J. Wiese for skillful experimental help in the analysis of
the compounds.

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R. Csuk et al. / Tetrahedron Letters 54 (2013) 2274–2276
17. John, G.; Zhu, G. Y.; Li, J.; Dordick, J. S. Angew. Chem., Int. Ed. 2006, 45, 4772–
4775.
6B), 3.87 (m, 2H, C-5), 3.59-3.49 (m, 2H, H-3), 3.24 (ddd, J = 9.5, 5.5, 3.8 Hz, 2H,
H-2), 3.15–3.05 (m, 2H, H-4), 2.25 (t, J = 7.3 Hz, 4H, H-8), 2.14–2.08 (m, 4H, H-
9), 1.54–1.39 (m, 6H, H-17, C-19), 1.19 (m, 28 H, CH2, H-(C-10)–H(C-16)), 1.15–
1.06 (m, 4H, H-18), 0.83 (dd, J = 6.6, 1.4 Hz, 12H, H-20, H-21) ppm; 13C NMR
(125 MHz, DMSO-d6): d = 173.2 (C-7), 93.8 (C-1), 73.14 (C-3), 71.90 (C-2), 70.59
(C-4), 70.18 (C-5), 63.5 (C-6), 38.9 (C-18), 35.2 (C-9), 34.0 (C-8), 29.53, 29.50,
29.46, 29.44, 29.39, 28.87 (C-11–C-16), 27.8 (C-19), 27.2 (C-10), 24.9 (C-17),
22.98, 22.97 (C-20, C-21) ppm; analysis for C42H78O13 (791.06): C, 63.77; H,
9.94; found: C, 63.51; H, 10.03.; 7 mp 165–167 °C (lit. 166–168 °C: Ref. 13),
18. Compound 4 was obtained by a sequence starting from methyl 11-iodo-
undecanoate that was transformed into the corresponding ylide (TPP, NaOEt in
DMF) being reacted with isobutyraldehyde. The olefin was hydrogenated (H2,
PtO2, 25 °C, 45 psi, EtOH) followed by a saponification (KOH in EtOH) and
reaction of the 13-methyltetradecanoic acid with vinyl acetate (4 equiv) in the
presence of Hg(OAc)2.
19. In a typical experiment, to a solution of the vinyl carboxylate (5.3 mmol) and 1
dihydrate (1.8 mmol) in acetone (20 ml) Novozyme 435 (0.28 g) was added,
and the mixture was stirred at 45 °C until TLC (ethyl acetate/MeOH/water,
17:4:1) showed completion of the reaction (48–72 h). The mixture was filtered,
the solvents were removed, and the residue was subjected to chromatography
to afford the diesters. For the mono-acylations the Alcalase from Bacillus
[
a
]
D
ꢀ1.2 (c 0.32, MeOH), MS (ESI, MeOH): 605.2 (29%, [MꢀH]ꢀ, 651.9 (100%,
[M+HCO2]ꢀ); NMR as reported [Ref. 13]; 8 mp: 112–114 °C, [
a] +6.6 (c 0.4,
D
MeOH), MS (ESI, MeOH, LiCl): 573.3 (100%, [M+L]+, 589.2 (100%, [M+Na]+), 1H
NMR (400 MHz, DMSO-d6): d = 5.02 (d, J = 5.4 Hz, 2 H, C-4, H-40), 4.84 (d,
J = 3.7 Hz, 1H, H-1), 4.82 (d, J = 3.6 Hz, 1H, H-10), 4.75 (d, J = 4.7 Hz, 2H, H-3, H-
30), 4.65 (d, J = 6.1 Hz, 2H, H-2, H-20), 4.33 (t, J = 5.8 Hz, 1H, H-6’), 4.21 (dd,
J = 11.5, 1.4 Hz, 1H, H-6), 4.01 (m, 1H, H-6), 3.92–3.81 (m, 2H, H-5, H-50), 3.68–
3.58 (m, 2H, H-3, H-30), 3.53 (m, 1H, H-60), 3.45 (dd, J = 11.8, 5.8 Hz, H-60), 3.23
(m, 2H, H-2, H-20), 3.15–3.07 (m, 2H, H-4, H-40), 2.25 (t, J = 7.4 Hz, 2H, H-8),
1.47 (tt, J = 13.1, 6.6 Hz, 2H, H-9), 1.37–1.28 (m, 1H, H-19), 1.19–1.23 (m, 16H,
H-(C-10)–H-(C-17)), 1.15-1.08 (m, 2 H, H-18), 0.82 (d, J = 6.6 Hz, 6H, H-20, H-
21) ppm; 13C NMR (100 MHz, DMSO-d6): d = 173.5 (C-7), 93.60 (C-10), 93.48 (C-
1), 73.04 (C-30), 72.91 (C-3), 71.78 (C-50), 71.75 (C-20), 70.32 (C-2), 70.27 (C-40),
69.88 (C-4), 69.76 (C-5), 63.18 (C-6), 61.11 (C-60), 38.90 (C-18), 33.70 (C-8),
29.59, 29.31, 29.22, 29.17, 29.01, 28.94, 28.72 (C-11–C17), 29.00 (C-19), 26.9
(C-10), 24.4 (C-9), 22.7 (C20, C-21) ppm; analysis for C27H50O4 (566.68): C,
57.23; H, 8.89; found: C, 57.11; H, 8.98.
licheniformis was used. Selected analytical data: 5 mp: 154–155 °C, [
0.48, MeOH), MS (ESI, MeOH, LiCl): 877.6 (100%, [M+Li]+, 909.7 (44%,
[M+MeOH+Li]+), 1H NMR (500 MHz, DMSO-d6): d = 5.34–5.26 (m,
H,
a]D +6.4 (c
4
CH'CH, H-15, H-16), 5.04 (d, J = 5.4 Hz, 2H, H-4), 4.87 (d, J = 4.9 Hz, 2H, H-
3), 4.80 (d, J = 3.6 Hz, 2H, H-1), 4.74 (d, J = 6.1 Hz, 2H, H-2), 4.21 (dd, J = 11.6,
1.5 Hz, 2H, H-6A), 4.01 (dd, J = 12.2, 5.3 Hz, 2H, H-6B), 3.90–3.83 (m, 2H, H-5),
3.53 (dd, J = 9.2, 4.9 Hz, 2H, H-3), 3.24 (ddd, J = 9.7, 6.1, 3.7 Hz, 2H, H-2), 3.10
(dd, J = 9.3, 5.5 Hz, 2H, H-4), 2.24 (t, J = 7.4 Hz, H-8), 2.02–1.92 (m, 8H, H-14A,B
,
H-17A,B), 1.56–1.40 (m, 4H,H-9A,B), 1.32–1.17 (m, 40H, CH2 (H(C-10)-H-(C13),
H-(C18)–H-(C23)), 0.83 (t, J = 6.9 Hz, 6H, CH3, H-24) ppm; 13C NMR (125 MHz,
DMSO-d6): d = 172.8 (C-7), 129.73 and 129.70 (C-15, C-16), 93.4 (C-1), 72.85
(C-3), 71.56 (C-2), 70.25 (C-4), 69.82 (C-5), 63.2 (C-6), 33.7 (C-8), 31.4 (C-22),
29.19, 28.93, 28.78, 28.67, 28.57, 28.54 (CH2, C-10–C-13, C-18–C-21), 26.69,
26.67 (C-14, C-17), 24.60 (C-9), 22.2 (C-23), 14.1 (C-24) ppm; analysis for
20. Using prolonged reaction times led to significant deacylation of the starting
materials; the formation of traces of 2 was determined only by ESI-MS.
21. Jenkins, I. D.; Goren, M. B. Chem. Phys. Lipids 1986, 41, 225–235.
C
48H86O13 (871.19): C, 66.18; H, 9.95; found: C, 65.97; H, 7.02; 6 mp 163–
164 °C; [
a
]
D
+7.7 (c 0.4, MeOH), MS (ESI, MeOH, LiCl): 797.6 (100%, [M+Li]+,
22. Selected analytical data for 2: colorless gummy solid; [a] H
D +7.2 (c 0.2, MeOH), 1
814.5 (27%, [M+Na]+), 1H NMR (500 MHz, DMSO-d6): d = 5.04 (dd, J = 3.6,
1.7 Hz, H-4), 4.86 (d, J = 1.5 Hz, H-3), 4.81 (d, J = 3.6 Hz, 2 H, H-1), 4.75-4.72 (m,
2H, H-2), 4.22 (dd, J = 11.4, 1.5 Hz, 2H, H-6A), 4.01 (dd, J = 11.9, 5.5 Hz, 2H, H-
and 13C NMR as reported [refs 5 and 14], MS (ESI, MeOH): 837.6 (100%,
[M+Li]+).