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D. S. RADCHENKO ET AL.
J ¼ 8.0 Hz, 1H, 3-CH), 3.66 (s, 3H, COOCH3), 2.78 (quint, J ¼ 8.8 Hz, 1H, 1-CH),
2.49–2.55 (m, 2H, 2- and 4-CHH), 2.30–2.36 (m, 2H, 2- and 4-CHH); 13C NMR
(CDCl3), d: 174.0 (COOCH3), 52.0, 50.8, 32.6, 30.6. 10b: MS (m=z, EI): 124 (Mþ–
OCH3), 113 (Mþ–N3), 99, 87, 68, 59, 41 (COOCH3þ). Anal. calcd. for C6H9N3O2:
1
C 46.45, H 5.85, N 27.08, found C 46.28, H 5.87, N 27.24; H NMR (CDCl3), d:
4.14 (quint, J ¼ 7.8 Hz, 1H, 3-CH), 3.68 (s, 3H, COOCH3); 3.07–3.13 (m, 1H,
1-CH), 2.53–2.58 (m, 2H, 2- and 4-CHH), 2.29–2.34 (m, 2H, 2- and 4-CHH); 13C
NMR (CDCl3), d: 175.4 (COOCH3), 51.9, 49.4, 32.7, 32.1.
cis-3-Aminocyclobutanecarboxylic acid (1a)
Azide 10a (0.30 g, 1.9 mmol) was dissolved in methanol (5 mL); then 6 N HCl
(2 mL) and 10% palladium on charcoal were added to the solution. The resulting
mixture was stirred under 1 bar of hydrogen for 3 h, then the catalyst was filtered
off, and the solvent was removed under reduced pressure. The residue was dissolved
in 6 N HCl (5 mL) and refluxed upon stirring for 1 h, then evaporated in vacuum.
The residue was purified by ion-exchange chromatography (Amberlite1 IR-
120(plus) ion-exchange resin, 3.5% aqueous ammonia as an eluent) to give cis-3-
aminocyclobutanecarboxylic acid 1a (0.16 g, 1.4 mmol, 71%) as white powder:
mp > 250 ꢁC (dec.); Anal. calcd. for C5H9NO2: C 52.16, H 7.88, N 12.17, found C
1
51.93, H 7.96, N 12.01; H NMR (D2O), d: 3.66 (quint, J ¼ 8.0 Hz, 1H, 3-CH),
2.80 (quint, J ¼ 9.0 Hz, 1H, 1-CH), 2.49–2.54 (m, 2H, 2- and 4-CHH), 2.12–2.18
(m, 2H, 2- and 4-CHH); 13C NMR (D2O), d: 182.7 (COO–), 41.2 (3-CH), 33.9, 31.1.
trans-3-Aminocyclobutanecarboxylic acid (1b)
Compound 1b was obtained from azide 10b analogously to the cis-isomer in
67% (0.17 g) yield as white solid: mp > 250 ꢁC (dec.). Anal. calcd. for C5H9NO2:
1
C, 52.16; H, 7.88; N, 12.17; found C, 52.42; H, 8.10; N, 11.92. H NMR (D2O), d:
3.84 (quint, J ¼ 8.0 Hz, 1H, 3-CH), 3.06 (tt, J ¼ 10.3 Hz and 5.1 Hz, 1H, 1-CH),
2.47–2.53 (m, 2H, 2- and 4-CHH), 2.30–2.36 (m, 2H, 2- and 4-CHH); 13C NMR
(D2O), d: 183.3 (COOꢂ), 44.0 (3-CH), 35.2, 30.2.
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