Dedicated to Professor George Buchi on the occassion of his 60th birthday (ll.V.81)
SummaryEasily accessible dihydropyrans 9, 10, 12 and 19 are precursors for the synthesis of 6-substituted 5,6-dihydro-2 (2H)-pyranones and 6-substituted tetrahydro-2-pyranones. Syntheses of massoia lactone (3), argentilactone (5), tuberolactone (4) and jasmine lactone (2) from acrolein (6), acrolein dimer (7) or glutaraldehyde (16) are described.Introduction. -Saturated and unsaturated aliphatic &lactones occur in several food flavors and essential oils [l] as the metabolites of higher molecular weight unsaturated fatty acids. Owing to their specific odor impression and low threshold concentration they play an important role as flavoring materials, and therefore practical syntheses of these d-lactones are greatly demanded.Whereas 5-decanolide (1) as well as its homologs are readily accessible from the Baeyer-Villiger reaction of the corresponding 2-substituted cyclopentanones, this approach is cumbersome for lactones containing C, C-double bonds (cf. syntheses of jasmine lactone (=(7Z)-7-decen-2-olide; 2) [2]). Despite the relatively simple structure of 6-substituted 5,6-dihydro-2 (2H)-pyranones, only a few syntheses to selected lactones are known [3]. We therefore looked for a general synthetic approach to ( f )-massoia lactone (= 2-decen-5-olide; 3), ( f )-tuberolactone (= (72)-2,7-decadien-Solide; 4), and (f )-argentilactone (= (62)-2,6-dodecadien-5-olide; 5). The latter lactone 5 was isolated recently from the rhizomes of Aristolochia argentina [4], and its synthesis has not yet been reported.
