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 by n.m.r. spectroscopy. The conformational equilibria of the 1,2-trans peracetylated aldopentopyranosyl benzoates and perbenzoylated aldopentopyranosyl acetates in solution
Abstract 2,3,4-Tri- O -acetyl- d -aldopentopyranosyl benzoates having the β- ribo ( 1 ), α- arabino ( 2 ), β- xylo ( 3 ), and α- lyxo ( 4 ) configurations, and 2,3,4-tri- O -benzoyl- d -aldopentopyranosyl acetates having the β- ribo ( 5 ), α- arabino ( 6 ), β- xylo ( 7 ), and α- lyxo ( 8 ) configurations have been prepared, and their conformations studied in acetone- d 6 or chloroform- d by n.m.r. spectroscopy at room temperature. Comparison of the results with similar data for the eight d -aldopentopyranose tetraacetates and tetrabenzoates indicates that the axial-directing effects of the OAc and OBz groups at C-1 are not independent of the total stereochemistry, nor are they independent of the nature of the acyloxy groups at C-2, 3, and 4. A concept of attractive interactions between syn -diaxial benzoyloxy groups provides a rationalization of the quantitative trends observed. The signal field-position of an acetyl group at O-1 is not subject to a strong upfield shift by the presence of benzoyloxy groups at C-2,3, and 4, nor does a 1- O -benzoyl group cause specific shielding of acetoxy groups at C-2, 3, and 4.