Taxane diterpenes synthesis

Benchikh le-Hocine, M., Do Khac, D., Fetizon, M. Model studies in taxane diterpene synthesis. Part III. Synth. Commun. 1992, 22, 245-255. 

Harriman GCB, Jalluri RK, Grunewald GL, Vander Velde DG, Georg GI (1995) The Chemistry of the Taxane Diterpene Stereoselective Synthesis of 10-Deacetoxy-... 

Entries 10 to 14 show reactions involving acetals. Interestingly, Entry 10 shows much-reduced stereoselectivity compared to the corresponding reaction of the aldehyde (The BF3-catalyzed reaction of the aldehyde is reported to be 24 1 in favor of the anti product ref. 80, p. 91). There are no stereochemical issues in Entries 11 or 12. Entry 13, involving two cyclic reactants, gave a 2 1 mixture of stereoisomers. Entry Mis a step in a synthesis directed toward the taxane group of diterpenes. Four stereoisomeric products were produced, including the Z E isomers at the new enone double bond. 

This reaction can be used in synthesis of medium-sized rings by cleavage of specific bonds. An example of this reaction pattern can be seen in a fragmentation used to construct the ring structure found in the taxane group of diterpenes. 

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