Palladium catalyzed alkylative cyclization useful in synthesis of vitamin D and analogues
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsBarry M. Trost, Jacques Dumas
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Abstract
An alkylative cycloaddition method is provided that is particularly useful for the synthesis of many of the Vitamin D analogues with differing side chains. Thus, a preferred synthesis is of Vitamin D analogues having a side chain R.sub.1 where a substantially geometrically pure first precursor having the structure ##STR1## and a second precursor are provided, the second precursor being a 1,7 enyne. These precursors are reacted in the presence of a palladium catalyst to form compounds having the structure ##STR2## where R.sub.2 hydrogen, hydroxyl, lower alkoxy, fluorine, or a protecting group, and R.sub.3 is hydrogen, hydroxyl, lower alkoxy, fluorine, or a protecting group.
Claims6
A method for the convergent synthesis of vitamin D analogues, represented by the following structural formula I having a Vitamin D analogues side chain R.sub.1 and a Vitamin D analogues ring A comprising:
- ##STR19## providing a first precursor having the structure ##STR20## and a second precursor, the second precursor being a 1,7 enyne;
- and, reacting the first and second precursors in the presence of a palladium catalyst to form a reaction product having a vitamin D analogue ring A derived from the second precursor via a new carbon-carbon bond.
Dependencies are inferred from the claim text.