Glycochimie synthétique pour les Sciences de la Vie : Contrôle de la

Séminaires & Conférences Chimie École Doctorale 459
Jeudi 16 Mai 2013, 13h45
Salle de Cours SC-25.01 – Université Montpellier II
Glycochimie synthétique pour les Sciences de la Vie : Contrôle de la sélectivité de quelques
réactions par des sels de fer
Jean-Marie Beau
Université Paris-Sud, ICMMO - CNRS, F-91405 Orsay ([email protected])
Centre de Recherche de Gif, ICSN - CNRS, F-91198 Gif-sur-Yvette ([email protected])
Iron salts have recently attracted considerable attention as inexpensive and environmentally
friendly agents in a wide range of selective processes in organic synthesis,1 and their use as Lewis
acid in carbohydrate chemistry is well-documented. We will report a few remarkable
transformations induced by iron (III) salts as a Lewis acid either under stoechiometric or catalytic
conditions. The results are very concise preparations of important glyco-constructs.
In connection with ongoing work at the interface of chemistry and biology, we will present:
- an unprecedented a one-pot cascade of transformations induced by iron(III)-chloride
hexahydrate, including acetal
FeCl3.6H2O,
Me
removal / C-C double bond
OH MeO OMe
CH2Cl2
Oi-Pr
isomerization / cyclization to a
O
N
O
87%
CO2i-Pr
dihydropyran / oxazoline
NHAc
O
formation on chiral substrates
derived from the threecomponent borono-Mannich Petasis reaction.2
- a regioselective one-pot protection of carbohydrates, optimized on D-glucopyranosides, by using
stable iron(III) chloride
Ph
hexahydrate a single
OH
O
1. TMSCl, pyridine
O
O
OH
Ph
O HO
O
catalyst in a single HO
O
HO
3
O
2.
PhCHO,
Et
SiH
Ph
reaction vessel. Different
HOO O OH 5 mol% of FeCl3.6H O
AcO O O O
3
2
Ph
room
temperature
building blocks, disthen Ac2O
41%
HO
AcO
playing different protecting group patterns are
obtained in a single flask by fine-tuning the reaction conditions. This approach circumvents the
necessity of carrying out the time-consuming isolation and purification of intermediates.
- the use of catalytic amounts of Fe(III) triflate.solvate for the efficient activation of the readily
available the βOAc
Catalytic
O
penta acetate of
OAc
AcO
OH
Fe(OTf)3.DMSO
O
AcO
O
O
N-acetyl glucosa- AcO
+ BnO
AcHN
OAc
AcO
BnO
TTBP, CH2Cl2,
O
BnO
mine in the direct
NHAc
BnOOMe µw, 80°C, 45 min
BnO
and highly selec98%
BnOOMe
tive synthesis of
the important GlcNAc β-glycoside motifs.4
1
Selected reviews: (a) C. Bolm, J. Legros, J. Le Paih, L. Zani, Chem. Rev. 2004, 104, 6217; (b) D. Diaz, P. Miranda,
J. Padrón, V. Martín, Curr. Org. Chem. 2006, 10, 457; (c) D. Sherry, A. Fürstner, Acc. Chem. Res. 2008, 41, 1500;
(d) E. B. Bauer, Curr. Org. Chem., 2008, 12, 1341.
2
J.-F. Soulé, A. Mathieu, S. Norsikian, J.-M. Beau, Org. Lett. 2010, 12, 5322-5325.
3
Y. Bourdreux, A. Lemétais, D. Urban, J.-M. Beau, Chem. Comm. 2011, 47, 2146-2148.
4
A. Stévenin, F.-D. Boyer, J.-M. Beau, Eur. J. Org. Chem. 2012, 1699-1702.