275. Lignans from Myristica otoba. The structures of hydroxyotobain and iso-otobain

Abstract

Proton magnetic resonance studies have been made on hydroxyotobain and on iso-otobain, and their structures have been shown to be (11) and (VI), respectively. The conformations of the molecules and the configurations at the asymmetric centres have been obtained. The conformations and configurations in otobain, hydroxyotobain, iso-otobain, and galcatin are identical.

The structure of chicanine, a new lignan from Schisandra sp.

“…After chromatography on a silica gel column using hexanelether (5: 1) as eluant, the main product, (+)galcatin 14, was obtained (90mg) and crystallized as prisms from methanol, mp 11 1-1 13°C. This compound showed identity in all respects with data reported for (-)galcatin (7)(8)(9)(10) …”

Neolignans

“…The similarities in the structures of 2.1e and galcatin (2.1d) are reflected in their IH NMR spectra. On such evidence, the relative configurations at C-7, 8 and 8' of 2.1d; 2.1e, 2.4a and 2.4b are identical (142), thereby confirming the stereochemical relations derived for galcatin (2.1d) by other means (28,133 Isogalcatin (2.1e) was obtained after methylation of a mixture of natural phenols which may have included otobaphenol (2.1b). This, isolated in later years, had its structure confirmed by synthesis of the dehydrogenation product of the derived ethyl ether 36 (Chart 11) (88).…”

“…Isogalcatin would be a preferable name (3) for the compound 2.1e, originally designated iso-otobain (142). The similarities in the structures of 2.1e and galcatin (2.1d) are reflected in their IH NMR spectra.…”

Highly Enantioselective Rhodium‐Catalyzed Addition of Arylboroxines to Simple Aryl Ketones: Efficient Synthesis of Escitalopram

“…Chiral diaryl alkyl carbinol moieties exist in a number of therapeutic agents and natural products, such as the antidepressant escitalopram, antihistamine clemastine, cough suppressant chlophedianol, multi‐AGC kinase inhibitor AT13148, fungicide flutriafol, and lignan hydroxyotobain (Figure ). The efficient synthesis of these chiral tertiary alcohols have thus gained a great deal of attention.…”