Entandrophragma

An X-ray analysis of kulactone (61), from Melia azedarach, has confirmed" the trans- fusion of the y-lactone and the euphol C-20 configuration. The penta-hydroxytirucaIl-7-ene, sapelin F (62), has been obtained" from Entandrophragma... 

Sapelin A (69) and sapelin B (70) have been obtained" from Entandrophragma cylindricum (Meliaceae) and are further examples of the group of euphane or tirucallane derivatives which co-occur with, and are likely precursors of, tetranor-triterpenoids (see later). Sapelin A was readily correlated with bourjotinolone A (71 ). Sapelin B reacted with sodium periodate to give the dialdehyde (72) which was transformed successively by sodium amalgam and chromium trioxide into the y-lactone (73) previously obtained from sapelin A and bourjotinolone A. 

The structure of phragmalin (75), a complex limonoid from Entandrophragma caiidatum, has been determined by X-ray analysis." It is closely related to utilin (see Vol. I, p. 177) and occurs in combination with nicotinic and isobutyric acids. 

Chan W R, Taylor D R Yee T 1970 Triterpenoids from Entandrophragma cylindricum Sprague. Part I. Structures of sapelins A and B. J Chem Soc (C) 311-314... 

Subsequently, several other members of this group have been isolated although they remain confined so far to Entandrophragma and a few other closely related genera. All contain an orthoacetate, either at positions 8, 9, 14 or at 1, 8, 9. The 1, 8,9 orthoacetates are completely resistant to alkaline hydrolysis, but the 8,9,14-derivatives are readily hydrolysed with loss of the orthoacetate and P-furfuraldehyde (79), in a manner similar to the hydrolysis of gedunin. Presumably the reaction proceeds from the ring opened lactone. Loss of a proton from the C-17 hydroxyl then initiates a fragmentation reaction with loss of P-furfuraldehyde and the C-14 substituent and formation of a 13,14-double bond. With attack initiated in this way, complete hydrolysis of the orthoacetate follows. 

Triterpenoids from Entandrophragma cylindricum Sprague. Part II. The... 

Triterpenes from the Seed of Entandrophragma Species. Phytochemistry 16,2029... 

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