S-Octalactone

If unlabeled precursors are added the investigation of pathways is mainly based on quantitative data and requires significant increases of metabolites. The use of deuterium labeled compounds offers the possibility to follow conversions of precursors with lower metaboli-zation rates, because the formed products can be detected based on their content of deuterium by using the more sensitive method of capillary gas chromatography-mass spectrometry. This technique revealed that two independent pathways starting from different precursors contribute to the formation of S-octalactone in pineapple. 

On the other hand deuterated -octalactone was also detected after addition of (Z)-d-octenoic acid-2,2-d2 to pineapple tissue (Figure 2). Hydration of the double bond followed by cyclization of the intermediates 4-hydroxyoctanoic acid-2,2-d2 and 5-hydroxyoctanoic acid-2,2-d2 leads to ir-octalactone-2,2-d2 and S-octalactone-2,2-d2, respectively. 

The formation of S-octalactone by three independent pathways (a) reduction of 5-oxoprecursors, (b) chain elongation of 3-hydroxy-hexanoate, and (c) hydration of (Z)-4-octenoic acid demonstrates the complexity of the biosynthesis of chiral compounds in natural systems. 

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