Glycosides of marine invertebrates. XVI. Cucumariogenin from glycosides of the holothurianCucumaria fraudatrix
A new genin of the holostane series has been isolated by the acid hydrolysis of the glycosidic fraction of the holothurianCucumaria fraudatrix. It has been shown that this genin is the native alycone of glycoside G1 from the same holothurian. The structure of the genin has been established as 16β-acetoxyholosta-7,24-dien-3β-ol.
Chemical studies of marine invertebrates—II : Terpenoids—LVIII Griseogenin, a new triterpenoid sapogenin of the sea cucumber halodeima grisea l.
Abstract Chemical degradation coupled with extensive physical measurements has lead to structure V for griseogenin. The correctness of this structure has been confirmed by correlation with the known sapogenin, 22,25-oxidoholothurinogenin (I).
Conformational studies on pyranoid sugar derivatives.
Abstract β- d -Ribopyranose tetraacetate ( 1 ) has been shown to exist, in acetone- d 6 at room temperature, as a 9:11 mixture of the 1C ( d ) and C1 ( d ) conformers in rapid equilibrium. The rate of chair-chair interconversion at −60° is 130 times per second. At −84°, a temperature at which n.m.r. spectral signals of the two separate conformers can be observed, the ratio of the 1C ( d ) to C1 ( d ) conformers is 2:1. For β- d -xylopyranose tetraacetate ( 2 ), in acetone- d 6 at room temperature, the all-axial, 1C ( d ) conformer exists in equilibrium with the all-equatorial, C1 ( d ) conformer to the extent of 1 part in 5. At −84°, the 1C ( d ) conformer was not detected.