11-Oxatricyclo decane

A mixture of 2-methyl-4-oxatricyclo[5.2.1.0.2,6]-decan-3-ol (63 g), pyridine (42 g), and acetic anhydride (51 g) were heated to 50°C for 5 hours and then concentrated. The residue was purified by distillation and 74 g product isolated as a colorless oil,... 

As the key precursor towards the realization of 1,7-epoxy cyclononanes and 1,8-epoxycyclodecanes, an 1 l-oxatricyclo[6.2.1.02,6]decane skeleton was constructed by using the Hoffmann [4+3] cycloaddition methodology <07EJO4383>. In Majetich s total synthesis of (-)-salviasperanol, the key step was the trifluoroacetic acid-promoted isomerization of a vinyl epoxide to 2,5-dihydrofuran, whose O-thiocarbamate was removed by radical reaction to produce salviasperanol dimethyl ether <07OL85>. The synthetic route is depicted below. 

The diallyl ether 56 derived from 1,3,5,6-tetrahydroxyxanthone undergoes tandem Claisen and Diels-Alder reactions to produce the caged 4-oxatricyclo[4.3.1.0]decan-2-one, a feature of a number of natural products obtained from Garcinia species <07OBC494, 07TL6586>. 

In K.C. Nicolaou s biomimetic synthesis of 1-O-methylforbesione, the construction of the 4-oxatricyclo[4.3.1.0]decan-2-one framework was achieved by using a double Claisen rearrangement that was followed by an intramolecular Diels-Alder reactionJ This one-pot biomimetic double Claisen rearrangement/intramolecular Diels-Alder reaction cascade afforded the natural product in 63% yield. 

Nicolaou, K. C., Li, J. "Biomimetic" cascade reactions in organic synthesis construction of 4-oxatricyclo[4.3.1.0]decan-2-one systems and total synthesis of 1-O-methylforbesione via tandem Claisen rearrangement/Diels-Alder reactions. Angew. Chem.. Int. Ed. Engl. 2001,40, 42644268. 

The ring oxygen in 4-oxatricyclo[5.2.1.02 6]decan-10-one (9) and 4-oxatricyclo [5.2.1.02,6]dec-8-en-10-one (10) is indeed held in such a rigid conformation that the electron donation from one of the two lone pair orbitals to C C1-C2 and ct C6-C7 appears a distinct possibility to support anrf-selectivity. Alternatively, the... 

Natural quinones such as komaroviquinone 117 have been reported to show in vitro trypanocidal activity. An efficient approach to the core skeleton of komaroviquinone was accomplished by the Rh(ll)-catalyzed reaction of the dimethyl-substituted diazo ester 115 to afford the oxatricyclo[6.3.1.0 ]do-decane skeleton 116 (Scheme 36) from an intramolecular [3+2]-cycloaddition... 

The biomimetic synthesis of morellin and related compounds is an example of the former case, and was first reported by Scheinmann and his coworkers [74]. Although the yield was not reported, the synthesis of 4-oxatricyclo[4.3.1.0]decan-2-one skeleton 95 through the tandem Claisen rearrangement/Diels-Alder reaction was achieved. 

Recently, the Nicolaou group reported the total synthesis of 1-O-methylforbe-sione having similar structural feature to morellin including 4-oxatricyclo[4.3.1.0]-decan-2-one. Although the tandem reaction gave some structural isomers, desired compound 97 was obtained as a major isomer [75]. 

Cantharidin analogue 38 was prepared by Matsumoto [21] employing analogous high-pressure-mediated Diels-Alder reactions of 3,4-dimethoxyfuran 35 with cyclohexene-l,2-dicarboxylic anhydrides 36a and cyclopentene-1,2-dicarboxylic anhydride 36a followed by catalytic hydrogenation produced ll-oxatricyclo[6.2.1.0 nui dec-ane-endo-2,7-dicarboxylic anhydrides and 10-oxatricyclo[5.2.1.0 ]decane-endo-2,6-dicarboxylic anhydride 37 albeit in low yields (Scheme 9). 

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