Synthesis and Ca2+ antagonistic activity of 2-[2-[(aminoalkyl)oxy]-5-methoxyphenyl]-3,4-dihydro-4-methyl-3-oxo-2H- 1,4-benzothiazines.
As an extension of the previous investigation (J. Med. Chem. 1988, 31, 919), we synthesized a series of 2-[2-[(aminoalkyl)oxy]-5-methoxyphenyl]-3,4-dihydro-4-methyl-3-oxo-2H- 1,4-benzothiazines (3) and evaluated their Ca2+ antagonistic activities. Ca2+ antagonistic activity was measured with isolated depolarized guinea pig taenia cecum. On the basis of their potent Ca2+ antagonistic activity, six benzothiazines were selected and further evaluated for their vasocardioselectivity. Among these six compounds, the key compound 15 [3,4-dihydro-2-[5-methoxy-2-[3-[N-methyl-N-[2-[3,4- (methylenedioxy)phenoxy]ethyl]amino]propoxy]phenyl]-4-methyl-3-oxo- 2H-1,4-benzothiazine hydrogen fumarate] was recognized as having the lowest cardioselectivity. Following optical resolution, the absolute configuration of the compound's optically active enantiomer was determined by means of X-ray crystallography of a synthetic precursor (+)-4a. The Ca2+ antagonistic activity of 15 was found to reside primarily in (+)-15 (which was about 7 times more potent than (-)-15). The in vitro study showed that (+)-15 had a low cardioselectivity compared to verapamil and diltiazem. This result suggests that (+)-15 would exhibit less adverse effects due to cardiac inhibition than diltiazem and verapamil in therapeutic use.
Fujita
M
M
Central Research Laboratories, Santen Pharmaceutical Co., Ltd., Osaka, Japan.
Ito
S
S
Ota
A
A
Kato
N
N
Yamamoto
K
K
Kawashima
Y
Y
Yamauchi
H
H
Iwao
J
J
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D002121:Calcium Channel Blockers / Q000138:chemical synthesis*; D002432:Cecum / Q000187:drug effects / Q000502:physiology; D004110:Diltiazem / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D008297:Male; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009200:Myocardial Contraction / Q000187:drug effects*; D013329:Structure-Activity Relationship; D013843:Thiazines / Q000138:chemical synthesis* / Q000494:pharmacology; D014961:X-Ray Diffraction
D002121:Calcium Channel Blockers; D007202:Indicators and Reagents; D013843:Thiazines; D004110:Diltiazem