title: [A novel synthesis of olmesartan medoxomil and examination of its related impurities].
abstract: OBJECTIVE
  To develop a new synthetic route for olmesartan medoxomil.
  
  
  METHODS
  Olmesartan medoxomil was prepared from ethyl 4-(1-hydroxy-1-methylethyl)-2-propylimidazole-5-carboxylate via hydrolysis and lactonization to afford 4,4- dimethyl-2-propyl-4,6-dihydrofuro [3,4-d]-1H-imidazole-6-one which was condensed with 2-(triphenylmethyl)-5-[4'-(bromomethylbiphenyl)-2-yl] tetrazole, followed by esterification with 4-chloromethyl-5-methyl-1,3-dioxol-2-one, and deprotection. The chemical structure of the major impurity in condensation reaction is the regio-isomer in the imidazole moiety, and confirmed by single crystal X-ray diffraction. The corresponding regio-isomer of olmesartan medoxomil was synthesized from the impurity by similar method. Optimization of the condensation conditions reduced the impurity to a negligible quantity.
  
  
  RESULTS
  Synthesis of olmesartan medoxomil by the new route gave a product of 60% yield and above 99.0% purity. The content of olmesartan medoxomil regio-isomer was effectively controlled to less than 0.1%.
  
  
  CONCLUSIONS
  A novel synthetic route for olmesartan medoxomil was developed successfully. The olmesartan medoxomil regio-isomer is reported for the first time.
authors.affiliation: Shanghai Institute of Pharmaceutical Industry, Shanghai 200437, China.
authors.forename: Tai-Zhi
authors.initials: TZ
authors.lastname: Wu
authors.forename: Xiao-Hua
authors.initials: XH
authors.lastname: Liu
authors.forename: Fu-Li
authors.initials: FL
authors.lastname: Zhang
authors.forename: Mei-Hua
authors.initials: MH
authors.lastname: Xie
mesh_terms: D047228:Angiotensin II Type 1 Receptor Blockers / Q000138:chemical synthesis* / Q000737:chemistry; D000818:Animals; D000959:Antihypertensive Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D007093:Imidazoles / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D015394:Molecular Structure; D000068557:Olmesartan Medoxomil; D051381:Rats; D013237:Stereoisomerism; D013777:Tetrazoles / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D000959:Antihypertensive Agents; D007093:Imidazoles; D013777:Tetrazoles; D000068557:Olmesartan Medoxomil