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1H and 13C NMR assignments and stereochemistry of d,l-isospongiadiol and six spongian intermediates

✍ Scribed by Anthony A. Ribeiro; Zhongqi Shen; Ming Wang; Yongzheng Zhang; Phillip A. Zoretic

Publisher: John Wiley and Sons
Year: 1998
Tongue: English
Weight: 300 KB
Volume: 36
Category: Article
ISSN: 0749-1581
DOI: 10.1002/(sici)1097-458x(199805)36:5<325::aid-omr268>3.0.co;2-2

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✦ Synopsis

Long-range (LR COSY, RELAY, TOCSY, HMBC) and neighbor (COSY, HMQC) 2D correlation NMR methods were used in tandem to derive complete 1H and 13C NMR assignments for synthetic d,l-isospongiadiol and six spongian intermediates obtained from a novel free-radical tandem cyclization process. The 13C NMR spectra of synthetic d,l-isospongiadiol are identical with those reported previously for natural isospongiadiol, whereas the 1H NMR spectra reÑect solvent di †erences. NOESY and di †erence NOE data demonstrate that synthetic d,l-isospongiadiol and the spongian intermediates have the desired 19b-methylene and 18a-, 17b-and 20bmethyl stereoselectivity at the stereogenic centers, and that rings AÈC are in chair conformations.

1998 John ( Wiley & Sons, Ltd.

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