2223 SummarySix sesquiterpenoids, (2 R, 5 E)-2,12-epoxycaryophyll-5-ene (l), (2 R, 5 E)-caryophyll-Sen-12-a1 (2), (2 S, 5 E)-caryophyll-5-en-12-a1 (3), isospathulenol The compounds 5, 6 and mintsulfide (14) possess the rare C-skeleton C, for which the semisystematic name 'salvialane' is proposed. The sesquiterpenoids 1-5 are new.
The preparation of the vitispiranes 9 and 10, identified among the volatiles of vanilla, from the theaspiranes 1 and 2 via the intermediates 4 and 5 and the allyl alcohols 7 and 8, respectively, is described. The theaspiranes 1 and 2 can be obtained from the compounds 11–15 or 24–26.
SummaryThe preparation of the vitispiranes 9 and 10, identified among the volatiles of vanilla, from the theaspiranes 1 and 2 via the intermediates 4 and 5 and the allyl alcohols 7 and 8, respectively, is described. The theaspiranes 1 and 2 can be obtained from the compounds 11-15 or 24-26.Vitispirane') (9/10), one of the most recently discovered ionone-like spiro-ethers, was identified in the volatiles of grape juice and distilled grape spirits, and in table and fortified wines [I]. We found the diastereoisomers 9 and 10 of vitispirane to be important aroma components of vanilla. Gas-chromatographic (GC.) analysis of the volatiles of a vanilla extract on a glass capillary column UCON HB 5 100 revealed the presence of the mixture 9/10 in the region between acetophenone and 5-methylfurfural. It appeared in an incompletely resolved double peak in which the ratio of 9 and 10 was about 1:32). The isomers showed practically identical mass spectra [ 11.Since it was not possible to separate 9 and 10 by preparative GC., stereoselective synthesis was undertaken. The naturally occurring theaspiranes'), a mixture of the diastereoisomeric 1 and 2 [2-41 which unlike vitispirane (9/10) can be separated by fractional distillation, were the suitable starting material. Separate treatment of cisand trans-theaspirane (1 and 2, re~pectively)~) with m-chloroperbenzoic acid yielded varying proportions of the diastereoisomeric epoxides 3 and 4, and 5 and 6, respectively, which were separated [6]. When treated with aluminium triisopropoxide at 140°, the main epoxidation products 4 and 54) gave in excellent yield exclusively the racemic allyl alcohols 7 and ti5), respectively. 7 (m.p. 70-71"), when treated with cold POCl,/pyridine, yielded cis-vitispirane (9) in over 50% yield, its diastereol) *) 3, 4, 5,For systematic names see exper. part. The NMR. spectra of the natural products show that the discoverers [l] of vitispirane also had a mixture of diastereoisomers. We thank Dr. Williams for this information and the spectra. The configuration of the theaspiranes 1 and 2 has already been established by direct linking with the known cis-and trans-theaspirone, respectively [5]. These products were also isolated from tea flavour [4] (cf. also [7]). The optically active compounds have been prepared independently in the same way [8]. We thank Drs. Kaiser and Lumparsky for the communication of the conference manuscript.
SummaryA new strategy for the synthesis of muscone (1) using the OH-assisted Prim reaction for macrocyclic ring closure has been developed. The monoacetal 4 of (Z, E)-4,%dodecadienedial (3), easily obtainable from (Z, E, E)-1,5,9-cyclododecatriene (2), is treated with methallylmagnesium chloride, and the resulting C16-precursor 5 is subjected to acid-catalyzed cyclization in dilute ( 6 1%) solutions. This results in formation of the bicyclic dihydropyran derivatives 6 which directly yield muscone (1) on heating with a noble metal catalyst saturated with hydrogen. The five-step pathway proceeds with readily available starting materials in conventional steps and excellent overall yield (-40%). This new principle of macrocyclic ring formation has also been used successfully for the preparation of 3-methylcyclotridecanone (34) and should be generally applicable for other suitable ring systems.In the preceding communication Buchi & Wiiest describe a new method for the preparation of macrocyclic ketones by the direct coupling of a , o -C ,,-dialdehydes with 1,3-bis (dimethylphosphono)-2-propanone [ 11. In this way cyclopentadecanone (Exaltone@) is obtained in an elegant and novel manner.We now describe a new and direct pathway to muscone (1) from the same readily accessible C,,-dialdehydes [2], which is particularly efficient when (Z, E)-4,%dodecadienedial(3) (Scheme) is used. The key step is the acid-catalyzed cyclization of the (E, Z)-isomeric hydroxyacetals 5 to the bicyclic dihydropyran derivatives 6, in which the 16 C-and the 0-atoms are already positioned as in muscone (1).When carrying out the cyclization with p-toluenesulfonic acid in boiling toluene, the formation of 6 proceeds smoothly, attaining 75% yield, provided that the concentration of 5 is kept below -1%. substantial reductions in the yield due to an increase of higher molecular weight by-products is observed only if the concentration of 5 exceeds -1.5%.The final step is effected by heating the bicyclic ether 6 to 3 135" with H2-activated noble metal catalysts (Pd/C, Pt, etc.) in xylene in a N2/H2 mixture to give muscone (1) in ca. 75% yield. There is also formed ca. 15% of the saturated ether 18 which is stable under these conditions. A virtually complete conversion of the bicyclic ethers, including the saturated compound 18, into muscone (1) then
SummarySix unsaturated y-lactones, (2)-5-octen-4-olide (l), (Z)-5-decen-4-olide (2), (Z)-6-nonen-4-olide (3), (Z)-6-dodecen-4-olide (4), (Z, 2)-6,9-dodecadien-4-0lide (5), and tuberolide (6)') have been identified for the first time in tuberose absolute (from Polianthes tuberosa L.). All structures were corroborated by synthesis and all, except 3 and 4, are new.An improved method for the stereoselective synthesis of (k )-cis-bicyclo [4.3.0]-non-3-en-7-one (23) by an AlCl,-catalyzed Diels-A lder reaction is reported.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.