Vitamin A and Carotenoids

with the end ring double bond in the lowest locant. Hence it is considered as a
derivative of cyclohex-2-ene not cyclohex-3-ene namely 4-[18-(4-Hydroxy-2,6,6-
trimethyl-1-cyclohexenyl)-3,7,12,16-tetramethyloctadeca-1,3,5,7,9,11,13,15,17-
nonaenyl]-3,5,5-trimethyl-cyclohex-2-en-1-ol. Careful scrutiny of zeaxanthin
and lutein will show that there is an asymmetric carbon only on lutein.
Asymmetry rules are considered separately in section 1.6 because they apply to
both naming systems. Both hydroxyl groups on these xanthophylls are also on
asymmetric centres.