Hexadecanolide, preparation

Advent of ring-closing olefin metathesis reaction has influenced the synthetic strategy of pheromones very much. For example, the racemate of a macrolide pheromone such as (5Z,13S)-5-tetradecen-13-olide (29) (aggregation pheromone of the flat grain beetle, Cryptolestes pusillus) could readily be synthesized as shown in Scheme 42 [67]. Unfortunately, ( )-29 prepared by this method was a mixture of c/s, trans-isomers (Z/E=69 31). (S)-5-Hexadecanolide (27) was also synthesized by means of ring-closing olefin metathesis as shown in Scheme 43 [68]. 

R,6R) diastereoisomer (Scheme 7). Again, from 34 the (5R,6R) product 43 was obtained. Products 42 and 43 represent the two enantiomers of the proposed major component of a mosquito oviposi-tion attractant pheromone (18). The enantiomeric forms of 5-hexadecanolide, 44 and 45, the pheromone of Vespa orientalis, were obtained from the enantiomeric aldehydes 34 and 37 (19). All the compounds obtained up to this point have been prepared in both enantiomeric forms, starting from a single chiral material. 

Both y- and 5-keto acids are reduced to hydroxy acids, which directly cyclize to the corresponding lactones in the incubation media. The pheromone (/f)-(+)-hexadecanolide has been prepared in this way by reduction of the corresponding 5-keto acid (eq 7). ... 

It was mentioned above that the industry has carrying out synthetic research to find alternatives to the nitro and polycyclic musks. Another approach to this problem is the investigation of known macrocyclic ketones and lactones (24) in search of more efficient processes that could be practiced on larger scales than had previously been contemplated. Some of the materials that have received this sort of attention are muskalactone (79) (25), cyclopentadecanone (44), hexadecanolide (80) (26) as well as the dilactone ethylene bras-sylate (81) and its lower homolog prepared from dodecanedioic acid. Reaction scheme shows some of the chemistry that has been developed in connection with the new chemical, oxacyclohexadecen-2-one (77) and muskalactone (79). 

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