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N. Vázquez et al. / Tetrahedron Letters 52 (2011) 615–618
13. Briefly: the acid chloride derivative (2, 7, or 12) was dissolved in dry DCM
under an inert atmosphere and the mixture was cooled to 0 °C. A solution of
the corresponding amine ((S)-(ꢀ)-2-aminoethyl-1-ethylpyrrolidine for
compounds 3, 8, and 13 and (S)-(ꢀ)-2-aminoethyl-Boc-pyrrolidine for
compounds 4, 9, and 14) in dry DCM and anhydrous TEA were then
sequentially added. The reaction mixture was allowed to reach room
temperature and react until TLC analysis revealed complete consumption of
the starting material; after purification by silica gel column chromatography,
compounds 3, 4, 8, 9, 13, and 14 were obtained in overall yields of 75%, 86%,
70%, 81%, 46%, and 47%, respectively. See Supplementary data for details.
14. 1H NMR (CDCl3, 500 MHz): d 1.15 (s, 3H, CH3), 1.49 (br s, 1H, CH2–CHNEt), 1.78
(br s, 2H, CH2–CH2NEt), 1.93 (br s, 1H, CH2–CHNEt), 2.11–2.40 (m, 12H, BH,
CH2–CH3, CH2-NEt), 2.77 (br s, 2H, CH2–CH3, CH-NEt), 3.20–3.29 (m, 2H, CH2–
NH, CH2-NEt), 3.42 (br s, 1H, CH2-NH), 4.26 (s, 1H, CH-carborane); 13C NMR
(CDCl3, 125.77 MHz): d 13.97, 23.30, 28.46, 41.86, 48.41, 53.69, 56.94, 62.08,
72.20, 160.01; 11B NMR (CDCl3, 160.46 MHz, decoupled): d ꢀ13.52, ꢀ12.72,
ꢀ12.06, ꢀ8.78, ꢀ3.38; HRMS (ESI): m/z calcd for C10H26B10N2OH: 296.324
[M+H]+; found: 296.325.
decoupled): d ꢀ15.73, ꢀ13.42, ꢀ11.48, ꢀ10.95, ꢀ7.70, ꢀ5.46; HRMS (ESI): m/z
calcd for C13H30B10N2O3Na: 393.316 [M+Na]+; found: 393.317.
19. 1H NMR (CDCl3, 500 MHz): d 1.14–1.17 (t, 3H, CH3–CH2(NEt)), 1.47–1.53 (m,
1H, CH2–CHNEt), 1.76–1.80 (m, 2H, CH2–CH2NEt), 1.91–1.98 (m, 1H, CH2–
CHNEt), 2.09 (s, 3H, CH3-cage), 2.15–2.52 (m, 10H, BH), 2.25–2.36 (m, 2H, CH2–
CH3(NEt), CH2-NEt), 2.79–2.83 (m, 2H, CH–CH2NHCO, CH2–CH3(NEt)), 3.23–
3.31 (m, 2H, CH2-NEt, CH2-NHCO), 3.44–3.49 (m, 1H, CH2-NHCO), 7.44 (s, 1H,
NH); 13C NMR (CDCl3, 125.77 MHz): d 13.73, 23.25, 24.47, 28.50, 41.83, 48.70,
53.75, 62.50, 75.74, 75.96, 158.77; 11B NMR (CDCl3, 160.46 MHz, decoupled): d
ꢀ11.15, ꢀ9.92, ꢀ5.53, ꢀ1.91; HRMS (ESI): m/z calcd for
C11H28B10N2OH:
313.328 [M+H]+; found: 313.327.
20. 1H NMR (CDCl3, 500 MHz): d 1.48 (s, 9H, Boc), 1.58–1.62 (m, 1H, CH2–CHNBoc),
1.82–1.89 (m, 2H, CH2–CH2NBoc), 2.01–2.04 (m, 1H, CH2–CHNBoc), 2.07 (s, 3H,
CH3-cage), 2.11–2.54 (m, 10H, BH), 3.09–3.13 (m, 1H, CH2-NHCO), 3.30–3.40
(m, 3H, CH2-NHCO, CH2-NBoc), 4.06 (br s, 1H, CH–CH2NHCO), 8.60 (s, 1H, NH–
CO); 13C NMR (CDCl3, 125.77 MHz): d 24.23, 24.44, 28.68, 29.93, 47.50, 48.53,
55.72, 75.98, 76.21, 81.00, 157.29, 158.86; 11B NMR (CDCl3, 160.46 MHz,
decoupled): d ꢀ12.70, ꢀ11.17, ꢀ10.00, ꢀ6.71, ꢀ5.56, ꢀ2.02; HRMS (ESI): m/z
calcd for C14H32B10N2O3Na: 407.332 [M+Na]+; found: 407.329.
15. 1H NMR (CDCl3, 500 MHz): d 1.47 (s, 9H, Boc), 1.57–1.61 (br m, 1H, CH2–
CHNBoc), 1.81–1.87 (br m, 2H, CH2–CH2NBoc), 1.99–2.07 (br m, 1H, CH2–
CHNBoc), 2.15–2.40 (br s, 10H, BH), 3.09 (br s, 1H, CH2-NBoc), 3.30–3.42 (m,
3H, CH2–NH, CH2-NBoc), 4.04 (br s, 1H, CH-NBoc), 4.24 (s, 1H, CH-carborane),
8.54 (s, 1H, NH); 13C NMR (CDCl3, 125.77 MHz): d 24.20, 28.68, 29.90, 47.53,
48.53, 55.76, 57.15, 72.35, 81.04, 157.37, 160.22; 11B NMR (CDCl3, 160.46 MHz,
21. (a) Ohta, K.; Yamazaki, H.; Endo, Y. Tetrahedron Lett. 2006, 47, 1937–1940; (b)
Alekseyeva, E. S.; Batsanov, A. S.; Boyd, L. A.; Fox, M. A.; Hibbert, T. G.; Howard,
J. A. K.; MacBride, J. A. H.; Mackinnon, A.; Wade, K. Dalton Trans. 2003, 475–
482; (c) Cappelli, A.; Giorgi, G.; Anzini, M.; Vomero, S.; Ristori, S.; Rossi, C.;
Donati, A. Chem. Eur. J. 2004, 10, 3177–3183.
decoupled):
C
16. See Supplementary data.
d
ꢀ13.72, ꢀ12.56, ꢀ8.89, ꢀ3.47; HRMS (ESI): m/z calcd for
22. (a) Davidson, M. G.; Hibbert, T. G.; Howard, J. A. K.; Mackinnon, A.; Wade, K.
Chem. Commun. 1996, 2285–2286; (b) Godfrey, P. D.; Grigsby, W. J.; Nichols, P.
J.; Raston, C. L. J. Am. Chem. Soc. 1997, 119, 9283–9284; (c) Harakas, G.; Vu, T.;
Knobler, C. B.; Hawthorne, M. F. J. Am. Chem. Soc. 1998, 120, 6405–6406; (d)
Macias, R.; Rath, N. P.; Barton, L. J. Organomet. Chem. 1999, 581, 39–44.
23. UPLC/ESI-MS analyses were performed using an AQUITY UPLC separation
13H30B10N2O3Na: 390.327 [M+Na]+; found: 390.327.
17. 1H NMR (CDCl3, 500 MHz): d 1.08 (br s, 3H, CH3–CH2N), 1.41 (br s, 1H, CH2–
CHNEt), 1.57–1.70 (m, 2H, CH2–CH2NEt), 1.84 (br s, 1H, CH2–CHNEt), 2.14 (br s,
1H, CH2–N), 2.23 (br s, 1H, CH2-NEt), 2.07–2.78 (m, 9H, BH), 2.49 (br s, 1H, CH-
NEt), 2.68 (br s, 1H, CH2–N), 2.94 (s, 1H, BH), 2.99 (s, 1H, CH-carborane), 3.05
(br s, 1H, CH2-NHCO), 3.17 (br s, 1H, CH2-NEt), 3.34 (br s, 1H, CH2-NHCO), 6.69
(s, 1H, NH); 13C NMR (CDCl3, 125.77 MHz): d 14.42, 23.25, 28.42, 41.66, 48.27,
53.68, 54.99, 61.87, 76.08, 160.85; 11B NMR (CDCl3, 160.46 MHz, decoupled): d
ꢀ15.85, ꢀ13.40, ꢀ11.69, ꢀ11.02, ꢀ7.87, ꢀ5.88; HRMS (ESI): m/z calcd for
module coupled to
Manchester, UK). An Acquity BEH C18 column (1.7
a
LCT TOF Premier XE mass spectrometer (Waters,
m, 5 mm, 2.1 mm) was
l
used as the stationary phase. The elution buffers were A (methanol) and B
(water and 0.1% formic acid). The column was eluted with a linear gradient:
t = 0 min, 95% B; t = 3 min, 1% B; t = 4 min, 1% B; t = 5 min, 95% B. Total run was
C
10H26B10N2OH: 299.313 [M+H]+; found: 299.312.
5 min, injection volume was 5 lL and the flow rate 600 lL/min. The detection
18. 1H NMR (CDCl3, 500 MHz): d 1.43 (s, 9H, Boc), 1.56 (br s, 1H, CH2–CHNBoc),
1.79–1.81 (m, 2H, CH2–CH2NBoc), 1.92–1.98 (m, 1H, CH2–CHNBoc), 2.07–2.51
(m, 9H, BH), 2.89 (s, 1H, BH), 2.95–3.04 (m, 2H, CH2-NHCO, CH-carborane),
3.24–3.33 (m, 3H, CH2-NHCO, CH2-NBoc), 3.57 (br s, 1H, CH-NBoc), 7.95 (s, 1H,
NH–CO); 13C NMR (CDCl3, 125.77 MHz): d 24.08, 28.57, 29.71, 47.29, 47.98,
54.74, 55.61, 76.02, 80.54, 156.96, 161.02; 11B NMR (CDCl3, 160.46 MHz,
was carried out in positive ion mode, monitoring the most abundant isotope
peaks from the mass spectra (MꢀH+): compound
3 (C10H26B10N2O, m/
z = 299.31, retention time = 2.58 min), nido form of compound
(C10H25B9N2O, m/z = 288.29, retention time = 1.70 min), compound
3
8
(C10H26B10N2O, m/z = 299.31, retention time = 2.28 min) and compound 13
(C11H28B10N2O, m/z = 313.33, retention time = 2.65 min).