Sumnzary. 3-Methylthio-hexanol (3) and a mixture of cis-and 2raiis-2-methyl-4-propyl-l,3-oxathiane (6a and 6b) have been identified in a flavor concentrate of the yellow passion fruit of Hawaiian origin. Syntheses of these new flavor constituents are described.
Scheme 3. Diastereoselective reductions of ketone 1. a) LiAlH 4 (1.15 equiv), THF, À70 8C to À50 8C; b) Red-Al ¾ (3.0 equiv), THF, À70 8C to room temperature; c) BH 3 ¥SMe 2 (0.71 equiv), THF, room temperature. NOE NOE NOE 3 J (H a /H b ) = 5.6 Hz 3 J (H a /H b ) = 0 Scheme 7. Structure determination of acetonides 16 and 17: a) 2-methoxypropene, cat. TFA, DMF, 25 8C, 3 h.
SummaryIn view of the demonstration by Jaenicke et a/. that different Iris varieties produce enantiomeric irones [6], we complement our 1971 paper on the stereochemistry of the irones [3]. 1) We give what information we have on the origin of the Iris oil used in [3]; 2) we show that we and Ruzicka et a/. on whose degradation work our determination of the C(2)-configurations was based had the same irones in hand; 3) we summarize independent assignments of the C(2)-configurations and the relative configurations of the a-irones. 4) We also describe the identification of a trace of the 'missing' trans-yirone in our oil, and 5 ) revise the preferred conformation of the cis-a-irones in solution.
Summary. The synthesis of racemic stercoisomcric compounds with the 5,5,9-trimethyldecalin skeleton and an oxygen function at C(1), C(2) or C(3) is described1). h novel general onestep synthesis of 2-decalones by means of acid catalyzed cyclization of acyclic or monocyclic precursors has been developed.
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