Structure elucidation of [1,3]oxazolo[4,5-e][2,1]benzisoxazole and naphtho[1,2-d][1,3]- and phenanthro[9,10-d]oxazoles using gradient selected gHMBC, gHMQC and gHMQC-TOCSY NMR techniques
✍ Scribed by Alan R. Katritzky; Novruz G. Akhmedov; Zuoquan Wang; Vitaly A. Roznyatovsky; Aleksandr A. Shestopalov; C. Dennis Hall
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 363 KB
- Volume
- 41
- Category
- Article
- ISSN
- 0749-1581
- DOI
- 10.1002/mrc.1288
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✦ Synopsis
Abstract
Structure elucidation of compounds in the benzisoxazole series (1–6) and naphtho[1,2‐d][1,3]‐ (7–10) and phenanthro[9,10‐d][1,3]oxazole (11–14) series was accomplished using extensive 2D NMR spectroscopic studies including ^1^H–^1^H COSY, long‐ range ^1^H–^1^H COSY, ^1^H–^13^C COSY, gHMQC, gHMBC and gHMQC‐TOCSY experiments. The distinction between oxazole and isoxazole rings was made on the basis of the magnitude of heteronuclear one‐bond ^1^J~C2, H2~ (or ^1^J~C3, H3~) coupling constants. Complete analysis of the ^1^H NMR spectra of 11–14 was achieved by iterative calculations. Gradient selected gHMQC‐TOCSY spectra of phenanthro[9,10‐d][1,3]oxazoles 11–14 were obtained at different mixing times (12, 24, 36, 48 and 80 ms) to identify the spin system where the protons of phenanthrene ring at H‐5, H‐6 and at H‐9 and H‐7 and H‐8 were highly overlapping. Copyright © 2003 John Wiley & Sons, Ltd.