Ethyl jasmonates

A Michael addition of the silyl enolate was employed in a short synthesis of ( )-methyl jasmonate from cyclopentenone (eqs 9 and 10). This convergent scheme was carried out in three steps conjugate addition of methyl Q -(methyldiphenylsilyl)lithioacetate to cyclopentenone, alkylation of the resulting enolate with (Z)-l-bromopent-2-ene, and desilylation with potassium fluoride ( )-ethyl jasmonate was prepared in a similar fashion. In the conjugate addition step, the Q -(methyldiphenylsilyl)ester gave superior results to those obtained with the a-trimethylsilyl esters. 

As the alcohol 22 was available it was simply a case of putting in the ethyl group. Of course the alternative order of events might be better. Since the reduction to the ds-alkene can be done either before or after incorporation into the cis-jasmone skeleton, 22 was also transformed5 into the propargylic bromide 24. 

Apple flavor The sometimes marked differences between aromas of individual varieties of apples are mainly due to quantitative variations in the composition of apple flavor substances. Key components are ethyl (+)-2-methylbutanoate and other esters of 2-methylbutanoic acid, in addition to ethyl and hexyl bu-tanoates, hexyl acetate, (E)-2- and (2)-3-hexenyl acetates (see fruit esters) and j3-damascenone. ( )-2- Hexenal, ( )-2- hexen-l-ol, and hexanal (see alka-nals) play a special role in A. f. These are trace aroma substances in intact apples. When the fruit cells are destroyed, the concentration of the Cg units increase strongly due to enzymatic processes. They are the main aroma components of apple juice. Accordingly, the aromas of fresh apples and apple juice differ markedly. Apricot flavor The typical aroma is due to the combined effects of numerous components with flowery and fruity characters these include linalool, 1-ter-pinen-4-ol, a-terpineol (see p-menthenols), 2-phen-ylethanol, a- and )8- ionones, /5- damascenone, and (Z)-jasmone for the flowery part together with fruit esters and lactones, e. g., 4-octanolide, 4- and 5-deca-nolide, 4-dodecanolide (see alkanolides), hexyl acetate and hexyl butanoate for the fruity part, rounded off by benzaldehyde. 

The first synthesis of a jasmonoid, namely dihydrojasmone, took place nine years before the structure of jasmone itself was established. This goal was achieved in 1924 by Hermann Staudinger and Leopold Ru icika in the course of their work on pyrethroids. [84] They carried out a Reformatzky reaction between ethyl laevulinate and ethyl 2-bromoheptanoate, and obtained the desired product, although in poor yield, by a Dieckmann cyclisation, followed by hydrolysis and decarbethoxylation (see next page). 

Allyl caproate Benzyl cinnamate Citral trans-trans-2,4-Decadienal Ethyl maltol Menthol cis-Methyl jasmonate Pine (Pinus pumilio) needle oil fragrance, fougeres detergents Dihydroterpinyl acetate fragrance, fresh outdoor scents 3-Hexenal... 

Fig. 13.7 Compounds present in male Grapholitha molesta hairpencils ethyl-tran -cinnamate (I), (-)-mellein (II), methyl-jasmonate (III), and methyl 2-epijasmonate (IV) (Baker eta/., 1981b).

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