The intermediate biphenyl aldehyde (XI) is prepared by two related methods. 4-Bromo-3-methylbenzonitrile (I) is oxidized to aldehyde (II) via radical bromination with N-bromosuccinimide/benzoyl peroxide, followed by treatment with trimethylamine N-oxide. Suzuki coupling of aryl bromide (II) with the pinacol boronate (III) affords biphenyl (IV). After protection of the aldehyde moiety of (IV) as the corresponding ethylene ketal (V), its cyano group is reduced to aldehyde (VI) employing DIBAL in THF. Subsequent reduction of (VI) with NaBH4 leads to alcohol (VII), which is further converted into the benzyl bromide (VIII) by means of CBr4/PPh3. Bromide (VIII) is condensed with the spiro imidazolone (IX) in the presence of NaH, to produce (X). Then acidic hydrolysis of the ethylene ketal and SEM groups of (X) gives rise to the intermediate aldehyde (XI)
Alternatively, reduction of 4-bromo-3-formylbenzonitrile ethylene ketal (XII) by means of DIBAL leads to aldehyde (XIII), which is further reduced to alcohol (XIV) with NaBH4. After bromination of (XIV) with CBr4/PPh3, the resultant benzyl bromide (XV) is condensed with the spiro imidazolone (IX), yielding (XVI). Then, acidic ketal hydrolysis in (XVI) furnishes aldehyde (XVII). Suzuki coupling between aryl bromide (XVII) and boronic acid (XVIII) gives biphenyl (XIX). The SEM group of (XIX) is then removed under acidic conditions to provide (XI)
Reductive amination of the biphenyl aldehyde (XI) with 4-amino-2,2-dimethylbutanoic acid (XX) in the presence of NaBH(OAc)3 produces aminoacid (XXI). This is finally cyclized to the corresponding lactam by treatment with DIC
Coupling of 2-bromobenzenesulfonyl chloride (I) with 5-amino-3,4-dimethylisoxazole (II) affords sulfonamide (III), which is further protected as the N-methoxyethoxymethyl derivative (IV) employing MEM-chloride in DMF. Lithiation of bromosulfonamide (IV), followed by treatment with trimethyl borate and acidic work up leads to the boronic acid intermediate (V). This is then subjected to Suzuki coupling with 4-bromo-3-methylbenzaldehyde (VI) to yield the biphenyl adduct (VII). After reduction of aldehyde (VII) to the benzylic alcohol (VIII) with NaBH4, reaction with methanesulfonyl chloride and diisopropylethylamine gives rise to the mesylate (IX) (1-3).
Mesylate (IX) is condensed with ethyl 2-propyl-4-ethylimidazole-5-carboxylate (X) yielding (XI). Simultaneous ester group hydrolysis and MEM group deprotection under acidic conditions gives rise to the imidazolecarboxylic acid (XII). This is finally coupled with methylamine via activation with CDI to produce the desired N-methyl carboxamide (1-3).