Ring-closing metathesis as a new strategy for the C-C coupling of monosaccharide derivatives via silicon tethering

Article abstract of DOI:10.1016/S0957-4166(99)00504-2

Suitable carbohydrate-derived terminal olefins have been coupled by ring-closing metathesis reaction following a silicon tethering strategy, generating very long contiguous chains of carbon atoms each equipped with specific stereochemistry and functionali

Full text of DOI:10.1016/S0957-4166(99)00504-2

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 11 (2000) 393–396
Ring-closing metathesis as a new strategy for the C–C coupling
of monosaccharide derivatives via silicon tethering
Michael Lobbel and Peter Köll ∗
Organic Chemistry Laboratory, Department of Chemistry, University of Oldenburg, Carl-von-Ossietzky-Straße 9-11,
26111 Oldenburg, Germany
Received 29 October 1999; accepted 11 November 1999
Abstract
Suitable carbohydrate-derived terminal olefins have been coupled by ring-closing metathesis reaction following
a silicon tethering strategy, generating very long contiguous chains of carbon atoms each equipped with specific
stereochemistry and functionality. © 2000 Elsevier Science Ltd. All rights reserved.
During the last couple of years the olefin metathesis reaction1 has been established as a significant
synthesis strategy in organic chemistry, in which unsatured carbon–carbon bonds are rearranged
in the presence of metal carbene complexes. Especially due to Grubbs2 and his benzylidene-
bis(tricyclohexylphosphine)dichlororuthenium catalyst 1, this approach has become a powerful
ring-closing tool for open chain dienes, mostly simultaneously delivering ethylene, thus shifting an
equilibration in one direction (Scheme 1). However, similar intermolecular reactions, which could lead
to very long carbon chains, proved to be difficult in many cases. Recently, Evans and Murthy3 reported
on a method to combine temporary silicon tethering methodology with the ring-closing metathesis
reaction in order to obtain C2-symmetric 1,4-diols. The advantage of this strategy is the clipping of
two allylic alcohols to form a diene, which can then be employed in a ring-closing metathesis reaction.
However, the olefin metathesis reaction has rarely been used in carbohydrate chemistry.4 Thus, we began
to adopt this strategy for the preparation of long chain monosaccharides.
Scheme 1.
∗
Corresponding author. E-mail: koell@uni.oldenburg.de
0957-4166/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(99)00504-2
tetasy 3139

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M. Lobbel, P. Köll / Tetrahedron: Asymmetry 11 (2000) 393–396
We started with the benzylidenation of commercially available methyl α-D-glucopyranoside 2
with benzaldehyde and anhydrous zinc chloride,5 as shown in Scheme 2, to first obtain methyl
4,6-O-benzylidene-α-D-glucopyranoside. The subsequent benzylation under standard conditions with
sodium hydride in DMF gave methyl 2,3-di-O-benzyl-4,6-O-benzylidene-α-D-glucopyranoside. Ne-
cessary cleavage of the benzylidene acetal was achieved by reduction employing LiAlH4/AlCl3 in
dichloromethane/ether.6 Finally, oxidation of the obtained intermediate, primary 6-OH-free, to aldehyde
3 succeeded with Dess–Martin periodinane7 in dichloromethane in high yield.
Scheme 2. Reagents: (i) ZnCl2, benzaldehyde (81%); (ii) benzyl bromide, sodium hydride in DMF (80%); (iii) LiAlH4/AlCl3
in dichloromethane/ether (75%); (iv) Dess–Martin periodinane in dichloromethane (92%)
Grignard-reaction8 of 3 (Scheme 3) at −60°C in THF with commercially available vinylmagnesium
bromide solution afforded the two allylic alcohols 4a as an oil and 4b as white crystals in 20 and 22%
yields, respectively, after column chromatography.
Scheme 3. Reagents: (i) 2.0 equiv. vinylmagnesium bromide solution, 1.0 M in THF
Treatment of 4a and 4b with diphenyldichlorosilane at 0°C for 20 h furnished the C2-symmetrical
bis-alkoxysilanes 5a and 5b in 18 and 30% isolated yields, respectively (Scheme 4). In the last step
we succeeded in ring-closing metathesis reaction using 15 mol% of Grubbs’ catalyst benzylidene-bis-
(tricyclohexylphosphine)dichlororuthenium 1 (40°C, 24 h) in a small amount of degassed dichlorome-
thane to give the seven-membered ring diphenyl silaketals 6a (31%) and 6b (19%). The structures af 6a
and 6b were corroborated as those of the other new compounds by 1H and 13C NMR spectroscopy.9
In conclusion, we were able to show a new strategy in carbohydrate chemistry for the coupling of
monosaccharides to obtain very long chain sugars, with properties almost unexplored.
References
1. For recent reviews, see: (a) Schuster, M.; Blechert, S. Angew. Chem. 1997, 109, 2124–2144; Angew. Chem., Int. Ed. Engl.
1997, 36, 2036–2056. (b) Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54, 4413–4450, and references cited therein.
2. Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996, 118, 100–110.
3. Evans, P. A.; Murthy, V. S. J. Org. Chem. 1998, 63, 6768–6769.
4. (a) Romyr, D.; Sanjoy, K. D.; Roy, R. Chem. Comm. 1998, 2437–2438. (b) Eder, E.; Hadwiger, P.; Leitner, A.; Stelzer,
F.; Stütz, E. 10th European Carbohydrate Symposium, July 11–16, 1999, PA 035. (c) Lobbel, M.; Köll, P. 10th European
Carbohydrate Symposium, July 11–16, 1999, PA 081.

M. Lobbel, P. Köll / Tetrahedron: Asymmetry 11 (2000) 393–396
395
Scheme 4. Reagents: (i) Ph2SiCl2, 2,6-lutidine; (ii) 15 mol% Grubbs’ catalyst 1 in dichloromethane
5. Wood Jr., H. B.; Diehl, H. W.; Fletcher Jr., H. G. J. Am. Chem. Soc. 1957, 79, 1986–1988.
6. Bhattacharjee, S. S.; Gorin, P. A. J. Can. J. Chem. 1969, 47, 1194–1206.
7. Speicher, A.; Bomm, V.; Eicher T. J. Prakt. Chem. 1996, 338, 588–590.
8. Czernecki, S.; Horns, S.; Valery, J.-M. J. Org. Chem. 1995, 60, 650–655.
1
2
9. Compound 6a: H NMR (500 MHz/CDCl3): δ=3.298 (s, 6H, OCH3), 3.480 (m, 6H, H2, H5, H4), 3.823 (d, 2H, J=10.4
Hz, CH2-Pha), 3.914 (dd, 2H, 3J3,2=9.4 Hz, 3J3,4=8.8 Hz, H3), 4.373 (d, 2H, J=10.9 Hz, CH2-Pha ), 4.539 (d, 2H, J1,2=3.3
2
3
0
2
2
2
0
Hz, H1), 4.581 (d, 2H, J=11.5 Hz, CH2-Phb), 4.668 (d, 2H, J=10.9 Hz, CH2-Phc), 4.688 (d, 2H, J=12.0 Hz, CH2-Phb ),
2
0
4.854 (d, 2H, J=10.9 Hz, CH2-Phc ), 5.039 (s, 2H, H6), 5.701 (s, 2H, H7), 6.720 (m, 4H, Ar-H), 7.124 (m, 6H, Ar-H),
7.298 (m, 26H, Ar-H), 7.688 (m, 4H, Ar-H); 13C NMR (CDCl3): δ=138.27–127.27 (Ar-C, C7), 97.73 (C1), 82.25 (C3), 80.00
(C2), 78.10 (C4), 75.88 (Bn-Cc), 74.55 (Bn-Ca), 74.02 (Bn-Cb), 70.25 (C6), 54.91 (OCH3). Compound 6b: H NMR (500
MHz/CDCl3): δ=3.399 (s, 6H, OCH3), 3.583 (dd, 2H, 3J2,1=3.3 Hz, 3J2,3=9.8 Hz, H2), 3.666 (d, 2H, 3J5,4=8.8 Hz, H5), 3.743
1

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M. Lobbel, P. Köll / Tetrahedron: Asymmetry 11 (2000) 393–396
(dd, 2H, 3J4,3=9.3 Hz, 3J4,5=8.8 Hz, H4), 3.867 (d, 2H, 2J=10.4 Hz, CH2-Pha), 3.996 (dd, 2H, 3J3,2=9.8 Hz, 3J3,4=9.3 Hz, H3),
2
2
3
0
4.559 (d, 2H, J=10.4 Hz, CH2-Pha ), 4.676 (d, 2H, J=11.9 Hz, CH2-Phb), 4.736 (d, 2H, J1,2=3.3 Hz, H1), 4.742 (d, 2H,
2
2
2
0
0
J=10.4 Hz, CH2-Phc), 4.810 (d, 2H, J=11.9 Hz, CH2-Phb ), 4.943 (d, 2H, J=10.4 Hz, CH2-Phc ), 5.209 (s, 2H, H6), 5.800
(s, 2H, H7), 6.720 (m, 4H, Ar-H), 7.124 (m, 6H, Ar-H), 7.298 (m, 26H, Ar-H), 7.688 (m, 4H, Ar-H); 13C NMR (CDCl3):
δ=138.54–127.30 (Ar-C, C7), 98.23 (C1), 82.20 (C3), 80.06 (C2), 77.32 (C4), 75.88 (Bn-Cc), 74.26 (Bn-Ca), 73.65 (C5),
73.41 (Bn-Cb), 68.70 (C6), 55.26 (OCH3).