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From optically pure 3-mercaptohexan-1-01s as key intermediates some chiral 1,3-0xathianes were synthesized and their structures elucidated by 'H and 13C NMR spectra. Sensory qualities of the optically pure isomers are given. 1,3-Oxathiane, chirale Fruchtarorna-VerhindungenMit optisch reinen 3-Mercaptohexan-1-olen als Schliisselsubstanzen werden einige chirale 1,3-0xa-thiane synthetisiert und ihre Strukturen mittels 'H-und "C-NMR-Spektren bestimmt. Die sensorischen Qualitaten der optisch reinen lsomere werden angegeben.3-(Methylthio)hexan-l-ol (2) and 2-methyl-4-propyl-I ,3-oxathiane (3), isolated and revealed in constitution by Winter et al.'") were found to be characteristic aroma compounds in the yellow passion fruit (Pussifloru edulis, f. flavicarpa). With optically pure 3-mercaptohexan-1-01s ( l a , 1 a') as key intermediates recently we succeeded in synthesizing all the four stereoisomers of 32-4). Some times later Pickenhagen et al.5) reported their efforts for enantioselective synthesis of (-)-and (+)-cis 3. In this work we present our latest results on structure function relationship of some chiral 1,3-oxathianes, well known fruit flavouringsIb), but up to the present without knowledge of their optical purity.By introduction of the acetyl rest the primary alcoholic function of 1 was protected and the 3-mercapto group esterified with chiral acyl chlorides [e. g . (-)-camphanoyl chloride2)] to give the diastereomeric thiol esters which were separated by liquid chromatography and transferred into the enantiomers l a and la' by reductive cleavage with LiAlH,. Absolute configurations of l a and la' were derived from 'H NMR spectroscopic behaviour of their hydratropic acid thiol esters2s3). This method proves the ( -) -( R ) and (+)-(S) configuration of the optical isomers l a and la', respectively. From cyclization of the key intermediates l a and la' with acetaldehyde result the optically pure cis/truns diastereomers 3a/3b and 3a'/3b' (10: I), respectively, which were separated by HRGC on SE 54 and in preparative scale by HPLC on C N phase. In a similar manner condensation of l a (la') with acetone or formaldehyde leads to the enantiomers of 2,2-dimethyl-4-propyl-l,3-oxathiane (4) or 4-propyl-I ,3-oxathiane (5), respectively. The main products 3a and 3a' of the 10: 1 mixtures of 3 were assumed to correspond to the thermodynamically more stable cis isomers'). But unambiguous conclusions for structure elucidation can be drawn from high-resolution 'H NMR spectroscopy (400 MHz).

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Durch Oxidation von cis‐2‐Methyl‐4‐propyl‐1,3‐oxathian (1) mit NaIO4 entstehen diastereomere Sulfoxide (äquatorial/axial‐Verhältnis 3:1), die flüssigkeitschromatographisch rein erhalten werden. Aus optisch reinem (2S,4R)‐1 werden die Sulfoxide 2 (75%) und 3 (25%), aus (2R,4S)‐1 die Sulfoxide 2′ (75%) und 3′ (25%) erhalten. Für 3 wurde eine Röntgenstrukturanalyse durchgeführt.

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