ABSTRACT
Bis(oxazoline)-palladium(II) catalyzed carbonylation of homopropargyl alcohols afforded acyclic methoxyacrylate 2 and 6-membered lactone 3a-k in good combined yield. In the case of propargyl alcohols, 5-membered lactones 3p, 3q, 16 were obtained in moderate yields. The one-pot synthesis of kawa lactones 3a, 3r, 3s and formal synthesis of dihydroxycystothiazole A and dihydroxycystothiazole C are presented. To elucidate the stereochemistry of (+)-annularin G and (-)-annularin H, the first asymmetric syntheses of these natural products were achieved.
Subject(s)
4-Butyrolactone/analogs & derivatives , Acrylates/chemistry , Biological Products/chemical synthesis , Palladium/chemistry , 4-Butyrolactone/chemical synthesis , 4-Butyrolactone/chemistry , Biological Products/chemistry , Catalysis , Lactones/chemical synthesis , Lactones/chemistry , StereoisomerismABSTRACT
Boxing clever: Direct conversion of a terminal alkyne group into a beta-methoxyacrylate is realized with the aid of the bis(oxazoline) ligand (box). Acetyl and ketal protecting groups, free hydroxy groups, and acid-sensitive glycosidic bonds are not affected under the reaction conditions. The one-pot synthesis of (+/-)-dihydrokawain from the homopropargyl alcohol is also achieved. tfa = trifluoroacetate.
Subject(s)
Alkynes/chemistry , Organoplatinum Compounds/chemistry , CatalysisABSTRACT
A total synthesis of (+)-bakkenolide-A was carried out via the key intermediate 4, which was prepared based on an asymmetric cyclization-carbonylation reaction established in our laboratory. Diastereoselective construction of the spirolactone moiety was achieved using Mitsuhashi's protocol as a key step.
Subject(s)
4-Butyrolactone/analogs & derivatives , Antineoplastic Agents, Phytogenic/chemical synthesis , 4-Butyrolactone/chemical synthesis , Cyclization , Indicators and Reagents , Magnetic Resonance Spectroscopy , Sesquiterpenes , Spironolactone/chemical synthesis , Spironolactone/chemistry , StereoisomerismABSTRACT
Palladium(II) catalyzed carbonylation of 1-ethynyl-1-propargyl acetate is described; in the absence of the bisoxazoline (box) ligand, the second triple bond did not react, affording cyclic orthoesters and . The use of meso-Phbox-Pd(ii) strikingly changed the course of the reaction, yielding bicyclic lactone by tandem carbonylative cyclization as a result of insertion of the second triple bond.
