71519-46-5Relevant academic research and scientific papers
Synthesis of (±)-gymnomitrol. Mn(OAc)3-initiated free-radical cyclization of alkynyl ketones
O'Neil, Steven V.,Quickley, Cheri A.,Snider, Barry B.
, p. 1970 - 1975 (1997)
Mn(OAc)3-initiated cyclization of alkynyl ketones in 9-19:1 EtOH/HOAc at 90°C is a useful cyclization procedure in favorable cases. Cyclization of (trimethylsilyl)alkynyl ketone 4e provides 62% of silylalkenes 26 and 27 in the key reaction of a seven-step (16% overall yield) synthesis of gymnomitrol (1) from readily available ketone 23. 9α-Hydroxygymnomitryl acetate (2) and 9-oxogymnomitryl acetate (3) have been prepared from gymnomitrol. Cyclization of propargyl cyclohexanones 39a-c provides bicyclic compounds 40-42 in 40-60% yield.
Stereoselective Total Synthesis of (+/-)-Gymnomitrol via Reduction-Alkylation of α-Cyano Ketones
Coates, Robert M.,Shach, Shrenik K.,Mason, Robert W.
, p. 2198 - 2208 (2007/10/02)
A 16-step total synthesis of the tricyclic sesquiterpene alcohol, gymnomitrol (1), from cis-tetrahydro-3a,6a-dimethyl-2,5(1H,3H)-pentalenedione (8) is described.Catalytic hydrogenation of the monoenol phosphate of 8 afforded the monoketone, cis-hexahydro-3a,6a-dimethyl-2(1H)pentalenone (7).Reduction-allylation of the α-(n-butylthio)methylene derivative of 7 gave allyl trimethyl ketone 14a having the allyl substituent in the exo orientation.The stereoisomer (19) of 14a was obtained by reduction-methylation af α-allyl α-cyano ketone 18.Ring closure was accomplished by conversion of the allyl trimethyl ketones, 14a and 19, to keto aldehydes 23 and 6, aldol cyclizations, and oxidation to give the isomeric bridged diketones 25 and 29, respectively.A more efficient synthesis of keto aldehyde 6 was based upon a Michael-like condensation of α-cyano ketone 16 with acrolein diethyl acetal which gave rise to α-ethoxyallyl α-cyano ketone 34.The enol ether in the side chain was converted to an ethylene acetal, the resulting α-cyano ketone (36) was subjected to reduction-methylation, and the acetal was hydrolyzed, affording keto aldehyde 6.Enol lactone 39, prepared from the corresponding keto acid (38), underwent efficient aldol cyclization upon reduction with diisobutylaluminium hydride, and the ketol so obtained was oxidized to bridged diketone 29.The synthesis of (+/-)-gymnomitrol was completed by regioselective addition of methyllithium to diketone 29, dehydration, and hydride reduction.
A Vinylsilane Route of (+/-)-Gymnomitrol
Paquette, Leo A.,Han, Yeun-Kwei
, p. 1831 - 1835 (2007/10/02)
Gymnomitrol, a sesquiterpenic alcohol of unusual structure, has been synthesized in an efficient and stereoselective manner.Selective ketalization of the bicyclooctanedione (4), followed by Wolf-Kishner reduction and deketalization, afforded the Cs symmetric ketone 5.Methylenation with paraformaldehyde and N-methylanilinium trifluoroacetate gave the exocyclic methylene derivative (6) which entered into copper-catalyzed 1,4 addition with the Grignard reagent from (E)-2-(bromovinyl)trimethylsilane and subsequent in situ methylation to deliver 12 in 66percent yield.Epoxidation and dilute acid hydrolysis of this intermediate furnished hydroxy ketone 15 directly.The coproducts 14a and 14b could also be converted to 15 which was oxidized to diketone 16.The final stages of the synthesis involved regioselective addition of methyllithium to 16, dehydration of the tertiary carbinol fuctionality, and ultimate lithium aluminium hydride reduction.
