The oxidation of mannitol diacetonide (I) with Pb(OAc)4 in benzene gives the glyceraldehyde acetonide (II), which is reductocondensed with benzylamine (III) by means of H2 over Pd/C in methanol to yield, after acidification with HCl, (S)-3-(benzylamino)propane-1,2-diol (IV). The cyclization of (IV) with benzaldehyde (V) in refluxing toluene affords the chiral oxazolidine (VI), which is treated with tosyl chloride and pyridine to provide the corresponding tosylate (VII). The condensation of (VII) with 4-[2-(cyclopropylmethoxy)ethyl]phenol (VIII) by means of NaH in DMF gives the phenolic ether (IX), which is treated with conc. HCl to open the oxazolidine ring and yield the chiral propanolamine (X). The alkylation of the secondary amino group of (X) with isopropyl iodide (XI) in refluxing ethanol affords the tertiary amine (XII), which is debenzylated by hydrogenation with H2 over Pd/C in ethanol to provide the target betaxolol.

The 3-(isopropylamino)propane-1,2(S)-diol (IV) intermediate has been obtained by two different methods: 1. The oxidation of 1,2,5,6-O-diisopropylidene-D-mannitol (I) with Pb(OAc)4 in THF gives (R)-2,3-O-isopropylideglyceraldehyde (II), which is reductocondensed with isopropylamine by means of H2 over Pd/C in methanol to yield (S)-3-(isopropylamino)-1,2-O-isopropylidenepropane-1,2-diol (III). The cleavage of the isopropylidene protecting group of (III) in hot 6N HCl affords the desired 3-(isopropylamino)propane-1,2-diol (IV) intermediate. 2. The reductocondensation of (R)-glyceraldehyde (V) with isopropylamine by means of H2 over Pd/C in methanol gives the desired 3-(isopropylamino)propane-1,2-diol (IV) intermediate. The cyclization of (IV) with benzaldehyde (VI) by heating at 150 C gives the oxazolidine (VII), which is treated with Ts-Cl and K2CO3 in pyridine to yield the tosylate (VIII). Finally, this compound is condensed with 4-[2-(cyclopropylmethoxy)ethyl]phenol (IX) by means of NaH in DMF and hydrolyzed with conc. aq. HCl to provide the target isopropanol derivative.

The 3-(isopropylamino)propane-1,2(S)-diol (IV) intermediate has been obtained by two different methods: 1. The oxidation of 1,2,5,6-O-diisopropylidene-D-mannitol (I) with Pb(OAc)4 in THF gives (R)-2,3-O-isopropylideglyceraldehyde (II), which is reductocondensed with isopropylamine by means of H2 over Pd/C in methanol to yield (S)-3-(isopropylamino)-1,2-O-isopropylidenepropane-1,2-diol (III). The cleavage of the isopropylidene protecting group of (III) in hot 6N HCl affords the desired 3-(isopropylamino)propane-1,2-diol (IV) intermediate. 2. The reductocondensation of (R)-glyceraldehyde (V) with isopropylamine by means of H2 over Pd/C in methanol gives the desired 3-(isopropylamino)propane-1,2-diol (IV) intermediate. The cyclization of (IV) with benzaldehyde (VI) by heating at 150 C gives the oxazolidine (VII), which is treated with Ts-Cl and K2CO3 in pyridine to yield the tosylate (VIII). Finally, this compound is condensed with 4-[2-(cyclopropylmethoxy)ethyl]phenol (IX) by means of NaH in DMF and hydrolyzed with conc. aq. HCl to provide the target isopropanol derivative.

The condensation of 4-[2-(cyclopropylmethoxy)ethyl]phenol (I) with epichlorohydrin (II) in pyridine gives the phenol ether (III), which is treated with HCl to open the epoxide ring and yield the racemic chloropropanol (IV). The optical resolution of (IV) by means of Lipase SP 435-L or AK and vinyl acetate (V) gives a mixture of (S)-acetate (S)-(VI) and unreacted (R)-alcohol (R)-(VI) that is easily separated. Finally, the chiral chloropropanol (R)-(VI) is treated with isopropylamine (VII) to afford the target betaxolol. The optical resolution of racemic betaxolol by means of the previously mentioned lipases has also been tried with poor results.

The 3-(isopropylamino)propane-1,2(S)-diol (IV) intermediate has been obtained by two different methods: 1. The oxidation of 1,2,5,6-O-diisopropylidene-D-mannitol (I) with Pb(OAc)4 in THF gives (R)-2,3-O-isopropylideglyceraldehyde (II), which is reductocondensed with isopropylamine by means of H2 over Pd/C in methanol to yield (S)-3-(isopropylamino)-1,2-O-isopropylidenepropane-1,2-diol (III). The cleavage of the isopropylidene protecting group of (III) in hot 6N HCl affords the desired 3-(isopropylamino)propane-1,2-diol (IV) intermediate. 2. The reductocondensation of (R)-glyceraldehyde (V) with isopropylamine by means of H2 over Pd/C in methanol gives the desired 3-(isopropylamino)propane-1,2-diol (IV) intermediate. The cyclization of (IV) with benzaldehyde (VI) by heating at 150 C gives the oxazolidine (VII), which is treated with Ts-Cl and K2CO3 in pyridine to yield the tosylate (VIII). Finally, this compound is condensed with 4-[2-(cyclopropylmethoxy)ethyl]phenol (IX) by means of NaH in DMF and hydrolyzed with conc. aq. HCl to provide the target isopropanol derivative.

The 3-(isopropylamino)propane-1,2(S)-diol (IV) intermediate has been obtained by two different methods: 1. The oxidation of 1,2,5,6-O-diisopropylidene-D-mannitol (I) with Pb(OAc)4 in THF gives (R)-2,3-O-isopropylideglyceraldehyde (II), which is reductocondensed with isopropylamine by means of H2 over Pd/C in methanol to yield (S)-3-(isopropylamino)-1,2-O-isopropylidenepropane-1,2-diol (III). The cleavage of the isopropylidene protecting group of (III) in hot 6N HCl affords the desired 3-(isopropylamino)propane-1,2-diol (IV) intermediate. 2. The reductocondensation of (R)-glyceraldehyde (V) with isopropylamine by means of H2 over Pd/C in methanol gives the desired 3-(isopropylamino)propane-1,2-diol (IV) intermediate. The cyclization of (IV) with benzaldehyde (VI) by heating at 150 C gives the oxazolidine (VII), which is treated with Ts-Cl and K2CO3 in pyridine to yield the tosylate (VIII). Finally, this compound is condensed with 4-[2-(cyclopropylmethoxy)ethyl]phenol (IX) by means of NaH in DMF and hydrolyzed with conc. aq. HCl to provide the target isopropanol derivative.