91237-33-1Relevant academic research and scientific papers
Synthetic bicyclic analogues of quassinoids
Lang'at, Caroline C.,Watt, Robert A.,Toth, Istvan,Phillipson, J. David
, p. 6857 - 6866 (1998)
A series of simple bicyclic analogues of quassinoids have been prepared including compounds with ring A typical of bruceolides and dehydrobruceolides. The synthesis of bicyclic compound 5 and tricyclic analogue 6 was accomplished by acid catalysed Robinson Annelation reaction. Hydroxyketone 9a and its 2-substituted analogues were also prepared to study the structure activity relationship.
A Synthetic Approach to the Quassinoids
Heathcock, Clayton H.,Mahaim, Cyril,Schlecht, Matthew F.,Utawanit, Thanin
, p. 3264 - 3274 (2007/10/02)
A synthetic route to the quassinoids has been developed.Two-stage annelation of 2-methylcyclohexanone with 1-chloro-3-pentanone gives tricyclic dienone 9 (60percent), which is oxidized by acetyl chromate in acetic acid to give dienedione 27 (80percent).Bisketalization of this material followed by hydrolysis of the conjugated enone ketals provides monoketal 30 (77percent), along with recovered 27.Ring C of 30 is functionalized by the Stiles and Reich methods to obtain the unsaturated keto ester 33 (73percent).The latter material reacts with ketene acetal 35 at 5-6 kbar and room temperature to give an adduct that is desilylated by treatment with aqueous KF; keto diester 39 is produced in 95percent yield.Epoxidation of 39 occurs smoothly with m-CPBA to give 46 (88percent), which is converted into allylic alcohol 40 by the two-step Sharpless procedure (78percent).Finally, pyridinium chlorochromate induces solvolytic cyclization of 40, affording 41 in 55percent yield.In the course of the investigation, it was also discovered that β-keto ester 46 is oxidized by m-CPBA to 47 in quantitative yield.
