` `
instruments belong to the ‘‘Servei de Ressonancia Magnetica
Nuclear’’ of the Universitat Autonoma de Barcelona. From
in THF (60 mL) and the solution was cooled to 0 1C with an ice
bath. At this temperature ethyl chloroformate (0.770 mL,
1.319 g cmꢀ3, 9.17 mmol) was added dropwise and the resulting
mixture was stirred at 0 1C for 30 min. Then (1S, 2R)-(ꢀ)-cis-
1-amino-2-indanol (1.20 g, 7.98 mmol) was added slowly at 0 1C.
The mixture was stirred for 1 h at 0 1C overnight at room
temperature and 3 h under reflux. After this, the mixture was
cooled to room temperature and diluted with AcOEt (20 mL).
The precipitated ammonium salt was filtered. Filtrates were
concentrated under reduced pressure and the residue recrystallized
in AcOEt/MeOH, thus obtaining the pure product 1 as a white
solid (2.53 g, 80%). Mp 175–176 1C; [a]D: ꢀ16.5 (c. 0.06 in
MeOH). IR nmax (ATR)/cmꢀ1 3429 (OH), 3293 (NH), 3072 and
3025 (QCH), 2938 (CH), 1682 and 1654 (CO), 1557 (ar C–C),
1466, 1428, 1359, 1180, 1132, 1083, 1052, 978, 732; dH
(600 MHz, DMSO-d6, rotamers mixture) 2.06–2.00 (1H, m,
OCCHCH2), 2.14–2.10 (0.5H, m, OCCHCH2), 2.21–2.17
(0.5H, m, OCCHCH2), 2.80 (0.5H, d, J 7.2 Hz, CCH2CHOH),
2.83 (0.5H, d, J 7.2, CCH2CHOH), 3.08–3.01 (1H, m,
CCH2CHOH), 3.44–3.39 (1H, m, NCH2), 3.52 (0.5H, dd,
J 11.1, J 4.8, NCH2), 3.55 (0.5H, dd, J 11.1, J 4.2, NCH2),
4.34–4.29 (1H, m, NCH2CHOH), 4.43–4.37 (1H, m,
NHCHCHOH), 4.52 (0.5H, t, J 12.0, NCHCO), 4.57 (0.5H,
t, J 7.8, NCHCO), 4.95 (0.5H, d, J 7.8, OH), 5.02 (0.5H, d, J 4.2,
OH), 5.16–5.05 (3H, m, PhCH2, OH), 5.17 (0.5H, dd, J 9.0,
J 5.4, OCNHCH), 5.21 (0.5H, dd, J 8.4, J 4.8, OCNHCH), 6.91
(0.5H, d, J 7.2, HAr), 7.00 (0.5H, t, J 7.8, HAr), 7.56–7.14 (8H, m,
`
´
the ‘‘Servei d’Analisi Quımica’’ of Universitat Autonoma de
Barcelona the following experimental data were acquired:
infrared spectra (IR), specific rotation (ORD) and high-
resolution mass-spectrometry (HR-MS). IR was recorded with
a Bruker Tensor27 with an ATR Golden. Specific rotation
values [a]D were obtained in a JASCO J-175 polarimeter at
589.6 nm and they are given in 10ꢀ1 deg cm2 ꢀ1. HR-MS
g
were determined using a microTOF-Q instrument with direct
injection of the sample. Elemental analyses were done by the
´
`
Serveis Cientıfico-Tecnics of the Universitat de Barcelona.
Elemental analyses of C, N and H were performed using an
elemental analyser EA-1108 CE Instrument of Thermo Fisher
Scientific with BBOT as an internal standard. The content of
Si was determined by ICP in a Perkin-Elmer Optima 3200RL
instrument. Melting points were determined using a Koffler-
Reichert apparatus and were not corrected. The enantiomeric
excess (ee) of the products was determined by chiral stationary
phase HPLC (chiral columns Daicel Chiralpak AD-H, Daicel
Chiralpak IC, Daicel Chiralcel OD) with a Waters 2960
instrument using a UV photodiode array detector. At the
Institut Charles Gerhardt of Montpellier, surface areas were
determined by the Brunauer–Emmet–Teller (BET) method
from N2 adsorption–desorption isotherms obtained with a
Micromeritics ASAP2020 analyzer after degassing samples
for 30 h at 55 1C under vacuum. The average pore diameter
was calculated by the BJH method. Thermogravimetric
HAr), 8.01–7.99 (1H, two d, J 8.4, J 9.0, OCNH); dC (62.5 MHz,
`
analysis of hybrid materials was done at ‘‘Institut de Ciencia
DMSO-d6, rotamers mixture) 26.5, 39.8, 40.6, 40.7, 41.0, 56.2,
56.6, 58.6, 58.8, 60.2, 60.8, 68.3, 68.8, 70.1, 70.8, 73.7, 74.0,
125.4, 125.7, 126.0, 127.7, 127.8, 128.7, 128.9, 129.0, 129.1,
129.5, 137.9, 138.0, 141.6, 141.9, 142.1, 156.7, 157.0, 175.1,
175.4; ESI-MS: calc. for C22H24N2O5Na: 419.1577, found:
419.1580.
dels Materials de Barcelona (ICMAB)’’ using a STA 449 F1
Netzsch instrument under atmospheric conditions. When
required, experiments were carried out with standard high
vacuum and Schlenk techniques. Chromatographic purifications
were performed under N2 pressure using 230–400 mesh silica gel
(flash chromatography).
N-Benzyloxycarbonyl-4-trans-hydroxy-L-proline 98%, (1S, 2R)-
(ꢀ)-cis-1-amino-2-indanol 99%, ethyl chloroformate 98%,
3-(isocyanatopropyl)triethoxysilane 95%, n-butylisocyanate
98%, tetrabutylammonium fluoride (TBAF, 1 M solution in
anhydrous THF), p-nitrobenzaldehyde 98%, 3-pentanone
98%, trans-b-nitrostyrene 98%, p-nitrobenzoic acid 99%,
Pd/C 10% wt and dry DMF were purchased from Sigma-
Aldrich. Cyclohexene 99% and cyclohexanone 99% were
obtained from Merck. All reagents and analytical grade solvents
were used as received except the 3-(isocyanatopropyl)triethoxy-
silane 95%, which was distilled under vacuum just before use.
Dry solvents and reagents were obtained following standard
procedures: 1,2-dichloroethane, pentane and triethylamine were
distilled over CaH2, THF and Et2O over Na/benzophenone,
and ethanol was distilled over Mg/I2. Distilled and deionized
water (MilliQ) was used for the sol–gel process. Triketone 9 was
prepared according to a previously described procedure.16
(2S, 4R)-Benzyl 4-(3-(triethoxysilyl)propylcarbamoyloxy)-2-
{(1S, 2R)-2-[3-(triethoxysilyl)propylcarbamoyloxy]-2,3-dihydro-
1H-inden-1-ylcarbamoyl}pyrrolidine-1-carboxylate, 2. Some
drops of dry DMF were added to a stirred suspension of 1
(1.50 g, 3.77 mmol) in dry ClCH2CH2Cl (5 mL) at 70 1C under
inert atmosphere, until a homogeneous solution was obtained.
Then, freshly distilled 3-(isocyanatopropyl)triethoxysilane
(3.80 mL, 0.990 g cmꢀ3, 15.2 mmol) and dry NEt3 (1.20 mL,
0.726 g cmꢀ3, 8.60 mmol) were added and the mixture was
stirred at 80 1C under an inert atmosphere of Ar for 48 h. Then
volatiles were removed under vacuum and the excess of
isocyanate was distilled off (0.03 mbar, 65 1C). The residue
was dissolved in a minimum amount of dry THF and the
product precipitated upon addition of dry diethyl ether. The
solid was filtered under a nitrogen atmosphere and washed
with dry pentane to give 2 as a pale brown powder (2.56 g,
76%). Mp 208–210 1C; [a]D +55.2 (c. 0.58 in EtOH); IR nmax
(ATR)/cmꢀ1 3319 and 3290 (NH), 2973, 2927 and 2884 (CH),
1687 and 1656 (CO), 1534, 1279, 1258, 1232, 1074 (SiO), 954,
767 and 734 (SiC); dH (400 MHz, DMSO-d6, rotamers
mixture) 0.51 (4H, pseudo t, J 8.4 Hz, CH2Si), 1.14 (18H, t,
J 7.0, OCH2CH3), 1.44 (4H, m, CH2CH2Si), 2.40–2.11 (2H, m,
OOCNCHCH2), 2.93 (5H, m, OCONHCH2, NHCHCHCH2),
3.17 (1H, m, NHCHCHOHCH2), 3.53 (2H, m, NCH2),
Syntheses
(2S, 4R)-Benzyl 4-hydroxy-2-((1S, 2R)-2-hydroxy-2,3-dihydro-
1H-inden-1-ylcarbamoyl)pyrrolidine-1-carboxylate, 1. N-Benzyl-
oxycarbonyl-4-trans-hydroxy-L-proline (2.12 g, 7.98 mmol) and
NEt3 99.5% (1.20 mL, 0.726 g cmꢀ3, 8.56 mmol) were dissolved
c
2770 New J. Chem., 2011, 35, 2766–2772
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011