Catalytic Asymmetric Synthesis of the <i>endo</i>-6-Aryl-8-oxabicyclo[3.2.1]oct-3-en-2-one Natural Product from <i>Ligusticum chuanxing</i> via 1,3-Dipolar Cycloaddition of a Formyl-Derived Carbonyl Ylide Using Rh<sub>2</sub>(<i>S</i>-TCPTTL)<sub>4</sub>
The reaction of a six-membered cyclic formyl-carbonyl ylide derived from α-diazo-β-ketoester with phenylacetylene derivatives under the catalysis of dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], Rh2(S-TCPTTL)4, provides cycloadducts containing an 8-oxabicyclo[3.2.1]octane ring system in up to 97% ee. This represents the first example of an enantioselective 1,3-dipolar cycloaddition
One-pot Synthesis of Furo[3,2-<i>c</i>]oxepin-4-one Derivatives by the CAN-mediated Reaction of<i>tert</i>-Butyl 2-(2-Hydroxytetrahydrofuran-2-yl)acetates with Alkenes
The reaction of tert-butyl 2-(2-hydroxytetrahydrofuran-2-yl)acetates with alkenes in the presence of 2 equivalents of cerium(IV) ammonium nitrate (CAN) is presented. 2,3,7,8-Tetrahydrofuro[3,2-c]oxepin-4(6H)-ones were formed in moderate to fair yields via 3+2-type dihydrofuran formation, followed by lactonization.
Biomimetic Synthesis of the Tetracyclic Core of Berkelic Acid
作者:Jingye Zhou、Barry B. Snider
DOI:10.1021/ol0704338
日期:2007.5.1
Acid-catalyzed condensation of 2,6-dihydroxybenzoic acid 3 with ketal aldehyde 14 in methanol at 25 degrees C, followed by CH2N2 esterification, gave a 4: 1: 4: 1 mixture of diastereomers 15b-18b in 60% yield. Equilibration of this mixture with TFA in CDCI3 provided tetracycle 15b ( 83% yield) with the complete skeleton of berkelic acid. A similar condensation at 0 degrees C afforded 15b - 18b and a reduction product 19b, which was probably formed by a 1,5-hydride shift.
Kobayashi, Kazuhiro; Minakawa, Hiroki; Sakurai, Hideo, Journal of the Chemical Society. Perkin transactions I, 1993, # 23, p. 3007 - 3010