Halogenation of allylamine (I) with either bromine or sulfuryl chloride produced the corresponding (halomethyl)aziridines (II). Subsequent treatment of (II) with n-butyllithium at -78 C yielded 1-azabicyclobutane (III). Opening of the bicyclic system of (III) with formic acid followed by acid hydrolysis provided 3-hydroxyazetidine (IV). This was condensed with 2-(methylsulfanyl)thiazoline (V) to give thiazolinylazetidine (VI). Alternatively, 3-hydroxyazetidine (IV) was condensed with 2-chloroethyl isothiocyanate (VII) to give the intermediate thiourea (VIII), which cyclized to the thiazoline (VI). Conversion of the hydroxyl group of (VI) into the thioacetate (IX) was carried out by either coupling with thioacetic acid under Mitsunobu conditions or by conversion to mesylate (X) followed by displacement with potassium thioacetate. The required thiol (XI) was then obtained from (IX) by basic hydrolysis of the thioacetate ester.

1-azabicyclobutane (III) was opened with thioacetic acid with concomitant N-acetylation yielding (XII). Further acid hydrolysis of (XII) gave 3-mercaptoazetidine (XIII). Condensation of (XIII) with either 2-(methylthio)thiazoline (V) or 2-chloroethyl isothiocyanate (VII) then produced thiazolinylazetidine (XI).

A further procedure consisted in the opening of 1-azabicyclobutane (III) with 2-mercaptothiazoline (XIV) to give (XV). Subsequent rearrangement of (XV) in the presence of methanesulfonic acid produced thiazolinyl azetidine (XI).

Condensation of (phosphoryloxy)carbapenem (XVI) with 3-mercapto-1-(1,3-thiazolin-2-yl)azetidine (XI) gave thioether (XVII). The p-nitrobenzyl ester group of (XVII) was then deprotected with Zn powder to afford the target carboxylic acid.

Halogenation of allylamine (I) with either bromine or sulfuryl chloride produced the corresponding (halomethyl)aziridines (II). Subsequent treatment of (II) with n-butyllithium at -78 C yielded 1-azabicyclobutane (III). Opening of the bicyclic system of (III) with formic acid followed by acid hydrolysis provided 3-hydroxyazetidine (IV). This was condensed with 2-(methylsulfanyl)thiazoline (V) to give thiazolinylazetidine (VI). Alternatively, 3-hydroxyazetidine (IV) was condensed with 2-chloroethyl isothiocyanate (VII) to give the intermediate thiourea (VIII), which cyclized to the thiazoline (VI). Conversion of the hydroxyl group of (VI) into the thioacetate (IX) was carried out by either coupling with thioacetic acid under Mitsunobu conditions or by conversion to mesylate (X) followed by displacement with potassium thioacetate. The required thiol (XI) was then obtained from (IX) by basic hydrolysis of the thioacetate ester.

1-azabicyclobutane (III) was opened with thioacetic acid with concomitant N-acetylation yielding (XII). Further acid hydrolysis of (XII) gave 3-mercaptoazetidine (XIII). Condensation of (XIII) with either 2-(methylthio)thiazoline (V) or 2-chloroethyl isothiocyanate (VII) then produced thiazolinylazetidine (XI).

A further procedure consisted in the opening of 1-azabicyclobutane (III) with 2-mercaptothiazoline (XIV) to give (XV). Subsequent rearrangement of (XV) in the presence of methanesulfonic acid produced thiazolinyl azetidine (XI).

Condensation of (phosphoryloxy)carbapenem (XVI) with 3-mercapto-1-(1,3-thiazolin-2-yl)azetidine (XI) gave thioether (XVII). The p-nitrobenzyl ester group of (XVII) was then deprotected with Zn powder to afford carboxylic acid. Finally, treatment of (XVIII) with either iodo or chloromethyl pivalate (XIX) produced the target compound.

Halogenation of allylamine (I) with either bromine or sulfuryl chloride produced the corresponding (halomethyl)aziridines (II). Subsequent treatment of (II) with n-butyllithium at -78 C yielded 1-azabicyclobutane (III). Opening of the bicyclic system of (III) with formic acid followed by acid hydrolysis provided 3-hydroxyazetidine (IV). This was condensed with 2-(methylsulfanyl)thiazoline (V) to give thiazolinylazetidine (VI). Alternatively, 3-hydroxyazetidine (IV) was condensed with 2-chloroethyl isothiocyanate (VII) to give the intermediate thiourea (VIII), which cyclized to the thiazoline (VI). Conversion of the hydroxyl group of (VI) into the thioacetate (IX) was carried out by either coupling with thioacetic acid under Mitsunobu conditions or by conversion to mesylate (X) followed by displacement with potassium thioacetate. The required thiol (XI) was then obtained from (IX) by basic hydrolysis of the thioacetate ester.

Condensation of (phosphoryloxy)carbapenem (XVI) with 3-mercapto-1-(1,3-thiazolin-2-yl)azetidine (XI) gave thioether (XVII). The p-nitrobenzyl ester group of (XVII) was then deprotected with Zn powder to afford the target carboxylic acid.

Halogenation of allylamine (I) with either bromine or sulfuryl chloride produced the corresponding (halomethyl)aziridines (II). Subsequent treatment of (II) with n-butyllithium at -78 C yielded 1-azabicyclobutane (III). Opening of the bicyclic system of (III) with formic acid followed by acid hydrolysis provided 3-hydroxyazetidine (IV). This was condensed with 2-(methylsulfanyl)thiazoline (V) to give thiazolinylazetidine (VI). Alternatively, 3-hydroxyazetidine (IV) was condensed with 2-chloroethyl isothiocyanate (VII) to give the intermediate thiourea (VIII), which cyclized to the thiazoline (VI). Conversion of the hydroxyl group of (VI) into the thioacetate (IX) was carried out by either coupling with thioacetic acid under Mitsunobu conditions or by conversion to mesylate (X) followed by displacement with potassium thioacetate. The required thiol (XI) was then obtained from (IX) by basic hydrolysis of the thioacetate ester.

Condensation of (phosphoryloxy)carbapenem (XVI) with 3-mercapto-1-(1,3-thiazolin-2-yl)azetidine (XI) gave thioether (XVII). The p-nitrobenzyl ester group of (XVII) was then deprotected with Zn powder to afford carboxylic acid. Finally, treatment of (XVIII) with either iodo or chloromethyl pivalate (XIX) produced the target compound.

Halogenation of allylamine (I) with either bromine or sulfuryl chloride produced the corresponding (halomethyl)aziridines (II). Subsequent treatment of (II) with n-butyllithium at -78 C yielded 1-azabicyclobutane (III). Opening of the bicyclic system of (III) with formic acid followed by acid hydrolysis provided 3-hydroxyazetidine (IV). This was condensed with 2-(methylsulfanyl)thiazoline (V) to give thiazolinylazetidine (VI). Alternatively, 3-hydroxyazetidine (IV) was condensed with 2-chloroethyl isothiocyanate (VII) to give the intermediate thiourea (VIII), which cyclized to the thiazoline (VI). Conversion of the hydroxyl group of (VI) into the thioacetate (IX) was carried out by either coupling with thioacetic acid under Mitsunobu conditions or by conversion to mesylate (X) followed by displacement with potassium thioacetate. The required thiol (XI) was then obtained from (IX) by basic hydrolysis of the thioacetate ester.

Condensation of (phosphoryloxy)carbapenem (XVI) with 3-mercapto-1-(1,3-thiazolin-2-yl)azetidine (XI) gave thioether (XVII). The p-nitrobenzyl ester group of (XVII) was then deprotected with Zn powder to afford the target carboxylic acid.

Halogenation of allylamine (I) with either bromine or sulfuryl chloride produced the corresponding (halomethyl)aziridines (II). Subsequent treatment of (II) with n-butyllithium at -78 C yielded 1-azabicyclobutane (III). Opening of the bicyclic system of (III) with formic acid followed by acid hydrolysis provided 3-hydroxyazetidine (IV). This was condensed with 2-(methylsulfanyl)thiazoline (V) to give thiazolinylazetidine (VI). Alternatively, 3-hydroxyazetidine (IV) was condensed with 2-chloroethyl isothiocyanate (VII) to give the intermediate thiourea (VIII), which cyclized to the thiazoline (VI). Conversion of the hydroxyl group of (VI) into the thioacetate (IX) was carried out by either coupling with thioacetic acid under Mitsunobu conditions or by conversion to mesylate (X) followed by displacement with potassium thioacetate. The required thiol (XI) was then obtained from (IX) by basic hydrolysis of the thioacetate ester.

Condensation of (phosphoryloxy)carbapenem (XVI) with 3-mercapto-1-(1,3-thiazolin-2-yl)azetidine (XI) gave thioether (XVII). The p-nitrobenzyl ester group of (XVII) was then deprotected with Zn powder to afford carboxylic acid. Finally, treatment of (XVIII) with either iodo or chloromethyl pivalate (XIX) produced the target compound.