Use of deuterium labelling to elucidate the stereochemistry of the initial step of the cyclization reaction in zeaxanthin biosynthesis in a Flavobacterium

Cyclization of lycopene in vivo in a Flavobacterium species, R1519, suspended in deuterium oxide medium gives (2S,2′S)-[2,2′-2H2]zeaxanthin, thus demonstrating that the initial proton (deuteron) attack in the cyclization reaction is on the re,re face of the C-1,2 double bond.