Ethyl 4-hydroxybenzoate (I) was alkylated with EtI and K2CO3 to afford ethyl ether (II). Subsequent hydrogenation of (II) over Rh/C produced ethyl 4-ethoxycyclohexane carboxylate (III) (1). Then, alkylation of (III) using benzyl chloromethyl ether and LDA gave the benzyloxymethyl compound (IV), which was hydrolyzed with ethanolic KOH to the carboxylic acid (V). Coupling of N-Boc-L-phenylalanine (VI) with benzylamine in the presence of EDC and HOBt produced amide (VII), and further acid deprotection of the Boc group of (VII) yielded phenylalanine-N-benzylamide (VIII). This was coupled with carboxylic acid (V) by means of DCC and HOAt to provide diamide (IX), which was debenzylated by catalytic hydrogenation yielding alcohol (X).

The mesylation of alcohol (X) yielded mesylate (XI), which was treated with potassium thioacetate to afford the thioacetate ester (XII). Finally, this thioacetate was hydrolyzed to the target thiol with NaOH.

Ethyl 4-hydroxybenzoate (I) was alkylated with EtI and K2CO3 to afford ethyl ether (II). Subsequent hydrogenation of (II) over Rh/C produced ethyl 4-ethoxycyclohexane carboxylate (III) (1). Then, alkylation of (II) using benzyl chloromethyl ether and LDA gave the benzyloxymethyl compound (IV), which was hydrolyzed with ethanolic KOH to the carboxylic acid (V). Coupling of N-Boc-L-phenylalanine (VI) with 3-pyridylamine in the presence of EDC and HOBt produced amide (VII), and further acid deprotection of the Boc group of (VII) yielded phenylalanine-N-(3-pyridyl)amide (VIII). This was coupled with carboxylic acid (V) by means of DCC and HOAt to provide diamide (IX), which was debenzylated by catalytic hydrogenation yielding alcohol (X).

The mesylation of alcohol (X) yielded mesylate (XI), which was treated with potassium thioacetate to afford the thioacetate ester (XII). Finally, this thioacetate was hydrolyzed to the target thiol with NaOH.

Ethyl 4-hydroxybenzoate (I) was alkylated with EtI and K2CO3 to afford ethyl ether (II). Subsequent hydrogenation of (II) over Rh/C produced ethyl 4-ethoxycyclohexane carboxylate (III) (1). Then, alkylation of (III) using benzyl chloromethyl ether and LDA gave the benzyloxymethyl compound (IV), which was hydrolyzed with ethanolic KOH to the carboxylic acid (V). Coupling of N-Boc-L-phenylalanine (VI) with benzylamine in the presence of EDC and HOBt produced amide (VII), and further acid deprotection of the Boc group of (VII) yielded phenylalanine-N-benzylamide (VIII). This was coupled with carboxylic acid (V) by means of DCC and HOAt to provide diamide (IX), which was debenzylated by catalytic hydrogenation yielding alcohol (X).

The mesylation of alcohol (X) yielded mesylate (XI), which was treated with potassium thioacetate to afford the thioacetate ester (XII). Finally, this thioacetate was hydrolyzed to the target thiol with NaOH.

Ethyl 4-hydroxybenzoate (I) was alkylated with EtI and K2CO3 to afford ethyl ether (II). Subsequent hydrogenation of (II) over Rh/C produced ethyl 4-ethoxycyclohexane carboxylate (III) (1). Then, alkylation of (II) using benzyl chloromethyl ether and LDA gave the benzyloxymethyl compound (IV), which was hydrolyzed with ethanolic KOH to the carboxylic acid (V). Coupling of N-Boc-L-phenylalanine (VI) with 3-pyridylamine in the presence of EDC and HOBt produced amide (VII), and further acid deprotection of the Boc group of (VII) yielded phenylalanine-N-(3-pyridyl)amide (VIII). This was coupled with carboxylic acid (V) by means of DCC and HOAt to provide diamide (IX), which was debenzylated by catalytic hydrogenation yielding alcohol (X).

The mesylation of alcohol (X) yielded mesylate (XI), which was treated with potassium thioacetate to afford the thioacetate ester (XII). Finally, this thioacetate was hydrolyzed to the target thiol with NaOH.