S-(Z,E)]-5-(1-hydroxy-2,6,6-trimethyl-4-oxocyclohex-2-en-1-yl)-3-methylpenta-2,4-dienoic acid

Abscisic acid ((S)​-​(+)​-​Abscisic acid) is a plant hormone which is as a growth inhibitor. Abscisic acid has been shown to regulate many aspects of plant growth and development including embryo maturation, seed dormancy, germination, cell division and elongation, floral induction, and responses to environmental stresses such as drought, salinity, cold, pathogen attack and UV radiation[1].
(+)-Abscisic acid (pure substance) is a colorless crystalline solid. It has a melting point of 160–161°C and sublimes at 120°C. The partition coefficients are 1.8 for the electrically neutral form and 0.94 for the ionic form. Its relative density is 1.21. The solubility in water is 3102 mg/L (at pH 4). The specific rotation is [α]²⁰D = +40.997° (c = 10.1 mg/mL in ethanol, at 20°C). The pKa is 4.61. It is soluble in chloroform, acetone, ethyl acetate, and diethyl ether but only sparingly soluble in benzene and water. The UV maximum absorption wavelength (in methanol) is 252 nm.
ChEBI: The naturally occurring (1'S)-(+) enantiomer of abscisic acid. It is an important sesquiterpenoid plant hormone which acts as a regulator of plant responses to environmental stresses such as drought and cold.
Crystallise the acid from CCl4/pet ether, EtOH/hexane and sublime it at 120o. Also purify it by dissolving ~30g in 30mL of EtOAc, adding 100mL of hexane and allow to crystallise overnight (yield 8.4g), m 156-158o, 161-163o, [] D +426o (c 0.005M H2SO4 in MeOH). [Cornforth et al. Nature (London) 206 715 1965, Soukemp et al. Helv Chim Acta 72 361 1989.] The RS-isomer was purified on a Kieselgel F254 plate with toluene/EtOAc/AcOH (50:50:3) and has m 188-190o [Cornforth et al. Aust J Chem 45 179 1992]. [Beilstein 17/3 V 13.]