Structures of Breynins A and B, Architecturally Complex, Orally Active Hypocholesterolemic Spiroketal Glycosides

Article abstract of DOI:10.1021/jo00045a022

Breynin A and its oxy congener, breynin B, were reisolated from the woody portion of the Taiwanese shrub Breynia officinalis Hemsl and formulated as 1 and 2, respectively.An arsenal of NMR techniques including DEPT, heteronuclear chemical shift correlation, 1H-1H COSY, and inverse long-range 1H-13C experiments were employed.Of particular importance for the NMR study was the preparation of breynin A undecaacetate (11).The analysis independently generated structure 1, confirming the assignment for breynin A recently reported by Ohkuma et al.However, spectral data and direct oxidation of breynin A to B demonstrated that the latter is not the hemithioacetal 8 as suggested by Ohkuma, but rather the isomeric sulfoxide 2.Improved purification of the Breynia glycosides via droplet counter-current distribution and HPLC is also described.