<unk>  contains L- and D-stereoisomers. Chemically, levocetirizine is the active L-enantiomer of<unk> . The drug is a member of the diphenylmethylpiperazine group of antihistamines. Analogues include cyclizine and hydroxyzine. Synthesis<unk>  synthesis: The 1-(4-chlorophenylmethyl)-piperazine is alkylated with methyl (2-chloroethoxy)-acetate in the presence of sodium carbonate and xylene solvent to produce the Sn2 substitution product in 28% yield. Saponification of the acetate ester is done by refluxing with potassium hydroxide in absolute ethanol to afford a 56% yield of the potassium salt intermediate. This is then hydrolyzed with aqueous HCl and extracted to give an 81% yield of the carboxylic acid product.
Cetirizine
Meclizine
Budesonide
Levocetirizine
Fexofenadine
Chloropyramine
Terfenadine
Ibuprofen