A. Ruderisch et al. / Tetrahedron: Asymmetry 12 (2001) 2025–2030
2029
in vacuo using a rotary evaporator. The resulting vis-
cous residue was dissolved in diethyl ether (50 mL) and
stored overnight at −10°C. The precipitate was sepa-
rated by filtration and washed with saturated sodium
hydrogen carbonate solution (25 mL) to remove the
remaining trifluoroacetic acid. This procedure was
repeated until the product did not show any acidic
reaction in a solution with methanol (pH* 6–7). The
product was dried for 24 h at 60°C under reduced
pressure (0.01 mbar). Yield: 12.2 g (97%), colourless
needles. Mp 172–174°C. [h]2D0 +32.0 (c 1, MeOH). Anal.
calcd for C9H20ON2: C, 62.73; H, 11.71; N, 16.27.
Found: C, 61.86; H, 10.93; N, 15.84%. 1H NMR
(DMSO-d6, 250 MHz, ppm): 8.07 (br d, -NH2), 3.50 (d,
1H, -CHNH2), 3.36 (s, 1H, CONH), 2.00 (m, 1H,
CH(CH3)2), 1.27 (s, 9H, C(CH3)3), 0.90 (d, 6H,
CH(CH3)2). MS (EI, 70 eV): 173 (m, 13%), 72 (C4H9,
100%).
brown residue was dissolved in diethyl ether (50 mL).
The precipitated salts were separated by filtration. The
organic phase was washed with water (2×20 mL). After
drying over magnesium sulfate the solvent was
removed. The resulting brown oil was purified by flash
chromatography using ethylacetate/n-hexane (3:1) as
eluent. The separated product was recrystallized from
n-hexane/diisopropylether and dried for 24 h at 0.01
mbar. Yield: (0.6 g, 68%), colourless crystals. Mp 155–
157. [h]2D0 −7.3 (c 1, MeOH). Anal. calcd for
C156H256N16O24: C, 68.39; H, 9.42; N, 8.18. Found: C,
67.45; H, 9.68; N, 8.13%. IR (KBr, cm−1): 3324, 3074,
2963, 2926, 2854, 1613, 1546, 1455, 1391, 1364, 1286,
1
1252, 1225, 1186, 1108, 1060, 909. H NMR (MeOD,
400 MHz, ppm):18 7.75, 7.69 (4H, Hg) 6.83 (s, 4H, HA),
6.42 (s, 4H, HB), 5.83–5.69 (m, 4H, HL), 5.03 (d, 4H,
HM(trans), J=18 Hz), 4.97 (d, 4H, HM(cis), J=10 Hz),
4.73 (t, 4H, HC), 4.42 (br s, 16H, He) 4.26 (m, 8H, Hd),
2.07 (m, 16H, Hc/HK), 1.94 (m, 8H, HD), 1.41–1.35 (m,
108H, HE-J/Ha), 0.98 (m, 48H, Hb). 13C NMR (MeOD,
100 MHz, ppm): 172.6, 172.3, 171.0, 170.6, 156.0,
140.0, 127.8, 114.4, 101.7, 70.5, 68.9, 60.3, 59.7, 52.3,
52.2, 37.5, 35.0, 32.9, 32.6, 31.4, 30.4, 30.2, 29.3, 20.0,
19.9, 19.2, 18.2. MS (FD, positive charged ions): calcd
for C156H256N16O24: 2739.7. Found: 2739.3 ([M]+),
2599.4 ([M−C10H19]+). MS (FD, negative charged
ions): calcd for C156H256N16O24: 2739.7. Found: 2739.9
([M]+), 2525.8 ([M−C11H21N2O2]+), 2312.9 ([M−
2(C11H21N2O2)]+). ESI-MS: 1392.0 ([M+2Na]2+), 1390.0
([M+H+K]2+), 1381.0 ([M+H+Na]2+), 1369.5 ([M+2H]2+).
HRMS: calcd: 1369.2481 ([M+2H]2+). Found:
1369.2483.
3.5. N-Bromoacetyl- -valine-tert-butylamide 4
L
Bromoacetic acid (9.96 g, 70 mmol) was dissolved in
dry dichloromethane (100 mL) in a 250 mL three-
necked round-bottomed flask. The solution was cooled
to −5°C. A solution of dicyclohexylcarbodiimide (DCC,
15.88 g, 77 mmol) in dry dichloromethane (10 mL) was
added dropwise to the cooled solution followed by
small portions of 3 (total: 12 g, 69.8 mmol). After
stirring the mixture for 6 h at room temperature the
solution was diluted to double its volume with
dichloromethane. The precipitated urea was removed
by filtration. The solvent was removed in vacuo. In
order to remove further amounts of urea the residue
was dissolved in ethyl acetate (50 mL) and heated to
50°C. The remaining urea was filtered off. This proce-
dure was repeated until no more urea was formed.
Subsequently n-pentane (100 mL) was added to the
solution. The solution was maintained at −5°C and the
precipitated 4 was collected by filtration and dried for
24 h at room temperature/0.01 mbar. Yield: 10.5 g
(51%) of a colourless powder. Mp 182–184°C. [h]D20
−24.3 (c 1, MeOH). Anal. calcd for C11H21O2N2Br: C,
45.19; H, 7.25; N, 9.59; Br, 27.02. Found: C, 44.63; H,
6.97; N, 9.72; Br, 25.09%. IR (KBr, cm−1): 3273, 3076,
2967, 1641, 1553, 1222, 656. 1H NMR (CDCl3, 250
MHz, ppm): 7.30 (d, 1H, -NH-), 6.0 (d, 1H, -NH-),
4.15 (dd, 1H, C*), 3.85 (s, 2H, Br-CH2-), 2.04 (dq, 1H,
-CH(CH3)2), 1.33 (s, 9H, -C(CH3)3), 0.93 (dd, 6H,
-CH(CH3)2). 13C NMR (CDCl3, 69.9 MHz, ppm):
169.7, 165.9, 59.4, 51.7, 34.0, 28.7, 19.1, 18.3. MS (EI,
70 eV): 295.2, 293.2 (M, 23%, respectively), 114.2 (M−
C4H9, 100%), 72.13 ([C4H10N]+, 84%).
3.7. Chirasil-Calix 6
Resorcinarene 5 (50 mg, 0.0182 mmol) and poly(90.7%
dimethyl- 9.3% hydromethyl)-siloxan (283 mg) were
dissolved in a mixture of dry tetrahydrofuran (5 mL)
and dry toluene (5 mL) under an inert atmosphere. A
solution of hexachloroplatinic acid (1 mg) in dry tetra-
hydrofuran (1 mL) was prepared separately and 100 mL
thereof were added to the reaction mixture. After stir-
ring the mixture under reflux for 72 h at 80°C, the
solution was allowed to cool to room temperature. The
solvent was removed and the residue was dissolved in
dry dichloromethane (5 mL). After adding 20 mL of
diethyl ether the mixture was kept at 5°C for 1 h. The
residual unreacted particles were separated by filtration
(pore 0.45 mm). Evaporation of the solvent afforded
Chirasil-Calix 6 (239 mg, 72%). To avoid cross-linking
of the polymer, the product was stored as a solution in
dry dichloromethane with exclusion of light. [h]2D0 −9.0
1
(c 1, CHCl3). H NMR (CDCl3, 250 MHz, ppm): 7.78,
3.6. Octakis-O-(acetyl-
L
-valine-tert-butylamide)-C-
6.77, 4.54, 4.31, 4.00, 2.15, 1.64, 1.28, 0.88, 0.06.
decenyl-resorcinarene 5
Amide 4 (1.46 g, 5 mmol) was added in small portions
to a suspension of 1 (0.44 g, 0.42 mmol) and potassium
carbonate (0.61 g, 4.42 mmol) in dry acetonitrile (20
mL). The reaction mixture was stirred for 24 h at 60°C.
Afterwards additional 4 (0.73 g, 2.5 mmol) was added.
The mixture was allowed to stir for a further 12 h at
60°C. After cooling, the solvent was evaporated and the
Acknowledgements
The authors thank Deutsche Forschungsgemeinschaft
and Fonds der Chemischen Industrie for financial sup-
port. We thank H.-J. Kolb, G. Nicholson, R. Su¨ßmuth,
M. Preschel and M. Vollprecht for valuable assistance.