S-[(2R)-3-chloro-2-methyl-3-oxopropyl] ethanethioate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: It has been found that the compound of the formula I can be prepared from L-proline in two reaction steps with a total yield of 67% through the acylation of L-proline, if L-proline is acylated with (R)-3-acetylthio-2-methylpropanoyl chloride of formula III: ##STR3## in the presence of KOH and potassium phosphate buffer at pH 7.5-8.5, and at a temperature of between about 0°-5° C. The resulting compound is 1-[3-acetylthio-2-(S)-methylpropanoyl]-L-proline, ##STR4## Compound IV, which also can be termed "S-acetyl captopril", can be acidified and then deblocked with sodium hydroxide to give captopril in yield of 67% relative to starting material of formula III, without any unwanted byproducts. of between about 0°-5° C

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: It has been found that the compound of the formula I can be prepared from L-proline in two reaction steps with a total yield of 67% through the acylation of L-proline, if L-proline is acylated with (R)-3-acetylthio-2-methylpropanoyl chloride of formula III: ##STR3## in the presence of KOH and potassium phosphate buffer at pH 7.5-8.5, and at a temperature of between about 0°-5° C. The resulting compound is 1-[3-acetylthio-2-(S)-methylpropanoyl]-L-proline, ##STR4## Compound IV, which also can be termed "S-acetyl captopril", can be acidified and then deblocked with sodium hydroxide to give captopril in yield of 67% relative to starting material of formula III, without any unwanted byproducts. of between about 0°-5° C

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: It has been found that the compound of the formula I can be prepared from L-proline in two reaction steps with a total yield of 67% through the acylation of L-proline, if L-proline is acylated with (R)-3-acetylthio-2-methylpropanoyl chloride of formula III: ##STR3## in the presence of KOH and potassium phosphate buffer at pH 7.5-8.5, and at a temperature of between about 0°-5° C. The resulting compound is 1-[3-acetylthio-2-(S)-methylpropanoyl]-L-proline, ##STR4## Compound IV, which also can be termed "S-acetyl captopril", can be acidified and then deblocked with sodium hydroxide to give captopril in yield of 67% relative to starting material of formula III, without any unwanted byproducts. of between about 0°-5° C

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: It has been found that the compound of the formula I can be prepared from L-proline in two reaction steps with a total yield of 67% through the acylation of L-proline, if L-proline is acylated with (R)-3-acetylthio-2-methylpropanoyl chloride of formula III: ##STR3## in the presence of KOH and potassium phosphate buffer at pH 7.5-8.5, and at a temperature of between about 0°-5° C. The resulting compound is 1-[3-acetylthio-2-(S)-methylpropanoyl]-L-proline, ##STR4## Compound IV, which also can be termed "S-acetyl captopril", can be acidified and then deblocked with sodium hydroxide to give captopril in yield of 67% relative to starting material of formula III, without any unwanted byproducts. of between about 0°-5° C