Acetamide stereoisomer
The compound of formula (I) is a water-stable, long acting β 2 -selective adrenoceptor agonist useful as a bronchodilator in the treatment of bronchoconstriction associated with reversible obstructive airways diseases and the like. Processes for making the compound of formula (I), as well as related intermediates, are disclosed.
1. A process for the preparation of
which comprises reacting a compound of general formula (II)
in which P 1 represents a hydrogen atom or a hydroxyl protecting group, with a compound of general formula (III)
in which P 2 represents a hydrogen atom or a trialkylsilyl and P 3 represents a benzylic amine protecting group, to afford a compound of general formula (IV)
or a salt thereof, followed by removing any protecting groups P 1 , P 2 and P 3 and, if desired, forming a pharmaceutically acceptable acid addition salt.
2. A process according to claim 1 wherein the trialkylsilyl is TBDMS.
3. A process for the preparation of
which comprises
a) reacting a compound of general formula (VII)
wherein Bn represents benzyl,
with boron tribromide to form a compound of general formula (VIII)
b) reacting said compound of general formula (VIII) with trialkylsilyl halide to form a compound of general formula (III)
in which P 2 represents a trialkylsilyl;
c) reacting said compound of general formula (III) with a compound of general formula (II)
in which P 1 represents a hydrogen atom or a hydroxyl protecting group, to afford a compound of general formula (IV)
or a salt thereof;
d) reducing with a source of hydrogen in the presence of a noble metal catalyst and treating with fluoride ion; and
e) if desired, forming a pharmaceutically acceptable acid addition salt.
4. A process according to claim 3 wherein the trialkylsilyl is TBDMS.