Lepidiline A → Lepidiline B

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Reaction Steps

The novel compound 1 was obtained as white needles in acetone, and its molecular formula of C19H19N2 was determined by HRFABMS. The IR spectrum of 1 showed a strong aromatic absorbance at 1560 cm−1. In 13C NMR spectrum of 1, only eight carbon signals were observed at δ 8.1 (q), 49.6 (t), 127.2 (s), 127.8 (d), 128.6 (d), 129.1 (d), 134.3 (s), and 135.5 (d), suggesting that the molecule of 1 is symmetrical to match the mass spectral data. Analysis of the 1H NMR signals at δ 5.41 (s), 7.31 (dd, J=8.8, 2.2 Hz), and 7.37-7.46 (m) and corresponding 13C NMR signals (gHMQC) at δ 49.6 (t), 127.8 (d), 128.6 (d), 129.1 (d), and 134.3 (s), indicated the appearance of a phenylmethylene group. This is supported by the COSY and gHMBC spectral data. A proton signal due to methyl group was observed as a singlet at δ 2.18, but the correlative carbon appeared in a very high field at δ 8.1 (q) in the gHMQC NMR experiment, similar to those of 1,3-di(4-fluorobenzyl)-4,5-dimethylimidazolium bromide, a synthesized product for the application as probes for intracellular pH determination. In the gHMBC NMR experiments of (1), the proton signal at 5.41 (s) exhibited other relevant cross-peaks at 127.2 (s) and 135.5 (d) attributable to C-2 and C-4 (5), respectively, apart from the ones of phenylmethylene moiety. On the other hand, H-2 showed two relevant cross-peaks at 49.6 (t) and 127.2 (s), assignable to the methylene group and C-4 (5), respectively.

Provenance & Evidence