Linaloyl derivatives

Since both neryl pyrophosphate and linaloyl pyrophosphate (or some equivalent species) (34) have been seriously considered as likely acyclic precursors to this family of monoterpenes, it is appropriate to examine first the cationic reactions of these two compounds. A great many investigations have shown that, while geranyl derivatives undergo substitution reactions in a fashion typical of an allylic substrate, both neryl and, less efficiently, linaloyl derivatives lead to cyclic products such as a-terpineol, and its dehydrated relatives limonene, and terpinolene... 

A remarkable feature of the cyclizations of linaloyl derivatives is the high stereoselectivity in the formation of a-terpineol. Thus, the hydrolysis of ( —) linaloyl phosphate (33-OP) affords (-h )-a-terpineol with an optical purity of 40% (79). The cyclization of linalool to optically active a-terpineol may also be carried out with sulfuric acid in acetic acid (81) and aqueous sulfuric acid (82). The a-terpinyl j9-nitrobenzoate produced in the hydrolysis of linaloyl /7-nitrobenzoate is obtained with an optical purity as high as 87% (80). These results require that cyclization occurs, at least in part, from an asymmetric transition state. 

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