Compound 14

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InChIKey BZEVXLCBXMQOOX-DABREVLYSA-N

Compound data: CIF

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

To a solution of 2.30 g (7.62 mmol, 1 eq.) azido alcohol 13 in MeOH (1.4 L) at 0 °C was added 390 μL (7.62 mmol, 1 eq.) Br₂. The reaction mixture was stirred under exclusion of light (to avoid radical reactions) for 12 h at 0 °C and concentrated in vacuo. The crude product was triturated with Et₂O (200 mL) and the formed precipitate was filtered off to yield 2.40 g (7.40 mmol, 97%) bromo pyrrolizidine hydrobromide 14 as colorless crystals. The filtrate was concentrated in vacuo to yield 1.20 g (7.24 mmol, 95%) carbonate 21. TLC (CHCl₃:MeOH:NH₄OH = 9:1:0.2), R_f = 0.65 (KMnO₄). ¹H NMR (MeOH-d₄, 400 MHz): δ= 4.86–4.82 (m, 1H), 4.38–4.31 (m, 1H), 4.29 (t, J=7.3 Hz, 1H), 4.11 (t, J=7.3 Hz, 1H), 3.90 (dd, J=6.1, 11.7 Hz, 1H), 3.67 (ddd, J=6.5, 7.5, 11.9 Hz, 1H), 3.49 (dt, J=6.5, 11.8 Hz, 1H), 3.20 (dd, J=9.1, 11.8 Hz, 1H), 2.72–2.56 (m, 2H). ¹³C NMR (CDCl₃, 100 MHz): δ= 74.1, 70.5, 68.6, 57.4, 53.4, 44.4, 34.8. IR (Diamond-ATR, neat) ν_max: 3308, 2528, 2458, 2110, 1471, 1381, 1284, 1129, 1063, 986, 860 669 cm^-1. [α]²⁵ _D + 22.0° (c= 0.41, MeOH). HRMS (ESI) calcd for C₇H₁₁BrN₄O [M+H]⁺: 247.0189; found: 247.0189. M.p.: 172 °C