The present invention relates to a process for preparing the hexanoic acid, 6-(nitrooxy)-, (1S,2E)-3-[(1R,2R,3S,5R)-2-[(2Z)-7-(ethylamino)-7-oxo-2-hepten-1-yl]-3,5-dihydroxycyclopentyl]-1-(2-phenylethyl)-2-propen-1-yl ester of formula (I). ##STR00001## In accordance with the present invention, the compound (I) can be efficiently prepared with high purity by coupling bimatoprost in a boronate protected form with 6-(nitrooxy)hexanoyl chloride and removing the boronate protecting group. The 6-(nitrooxy)hexanoyl chloride intermediate is prepared by ring-opening reaction of 2-caprolactone and subsequent nitration of the 6-hydroxyhexanoic acid potassium salt with a mixture of HNO.sub.3 and H.sub.2SO.sub.4 in dichloromethane.

The present invention relates to a process for preparing the hexanoic acid, 6-(nitrooxy)-, (1S,2E)-3-[(1R,2R,3S,5R)-2-[(2Z)-7-(ethylamino)-7-oxo-2-hepten-1-yl]-3,5-dihydroxycyclopentyl]-1-(2-phenylethyl)-2-propen-1-yl ester of formula (I). ##STR00001## In accordance with the present invention, the compound (I) can be efficiently prepared with high purity by coupling bimatoprost in a boronate protected form with 6-(nitrooxy)hexanoyl chloride and removing the boronate protecting group. The 6-(nitrooxy)hexanoyl chloride intermediate is prepared by ring-opening reaction of 2-caprolactone and subsequent nitration of the 6-hydroxyhexanoic acid potassium salt with a mixture of HNO.sub.3 and H.sub.2SO.sub.4 in dichloromethane.

The present invention relates to a process for preparing the hexanoic acid, 6-(nitrooxy)-, (1S,2E)-3-[(1R,2R,3S,5R)-2-[(2Z)-7-(ethylamino)-7-oxo-2-hepten-1-yl]-3,5-dihydroxycyclopentyl]-1-(2-phenylethyl)-2-propen-1-yl ester of formula (I). ##STR00001## In accordance with the present invention, the compound (I) can be efficiently prepared with high purity by coupling bimatoprost in a boronate protected form with 6-(nitrooxy)hexanoyl chloride and removing the boronate protecting group. The 6-(nitrooxy)hexanoyl chloride intermediate is prepared by ring-opening reaction of 2-caprolactone and subsequent nitration of the 6-hydroxyhexanoic acid potassium salt with a mixture of HNO.sub.3 and H.sub.2SO.sub.4 in dichloromethane.

The present invention relates to a process for preparing the hexanoic acid, 6-(nitrooxy)-, (1S,2E)-3-[(1R,2R,3S,5R)-2-[(2Z)-7-(ethylamino)-7-oxo-2-hepten-1-yl]-3,5-dihydroxycyclopentyl]-1-(2-phenylethyl)-2-propen-1-yl ester of formula (I).

##STR00001##

In accordance with the present invention, the compound (I) can be efficiently prepared with high purity by coupling bimatoprost in a boronate protected form with 6-(nitrooxy)hexanoyl chloride and removing the boronate protecting group.

The 6-(nitrooxy)hexanoyl chloride intermediate is prepared by ring-opening reaction of 2-caprolactone and subsequent nitration of the 6-hydroxyhexanoic acid potassium salt with a mixture of HNO.sub.3 and H.sub.2SO.sub.4 in dichloromethane.

The present invention relates to a process for preparing the hexanoic acid, 6-(nitrooxy)-, (1S,2E)-3-[(1R,2R,3S,5R)-2-[(2Z)-7-(ethylamino)-7-oxo-2-hepten-1-yl]-3,5-dihydroxycyclopentyl]-1-(2-phenylethyl)-2-propen-1-yl ester of formula (I).

##STR00001##

In accordance with the present invention, the compound (I) can be efficiently prepared with high purity by coupling bimatoprost in a boronate protected form with 6-(nitrooxy)hexanoyl chloride and removing the boronate protecting group.

The 6-(nitrooxy)hexanoyl chloride intermediate is prepared by ring-opening reaction of 2-caprolactone and subsequent nitration of the 6-hydroxyhexanoic acid potassium salt with a mixture of HNO.sub.3 and H.sub.2SO.sub.4 in dichloromethane.

A method for preparing a nitrate ester is provided. The method includes providing a first solution including a compound (which has at least one hydroxyl group) and a carboxylic acid having 2-5 carbon atoms; providing a second solution including nitric acid, acetic anhydride, and acetic acid; and transferring the first solution and the second solution to a microreactor, obtaining a nitrate ester after a residence time. In particular, the ratio of the weight of nitric acid to the total volume of the acetic anhydride and acetic acid is 1:1 to 1:3.5. The ratio of the molar amount of nitric acid to the hydroxyl group equivalent of the compound is from 1:1 to 15:1.

A method for preparing a nitrate ester is provided. The method includes providing a first solution including a compound (which has at least one hydroxyl group) and a carboxylic acid having 2-5 carbon atoms; providing a second solution including nitric acid, acetic anhydride, and acetic acid; and transferring the first solution and the second solution to a microreactor, obtaining a nitrate ester after a residence time. In particular, the ratio of the weight of nitric acid to the total volume of the acetic anhydride and acetic acid is 1:1 to 1:3.5. The ratio of the molar amount of nitric acid to the hydroxyl group equivalent of the compound is from 1:1 to 15:1.

A method for preparing a nitrate ester is provided. The method includes providing a first solution including a compound (which has at least one hydroxyl group) and a carboxylic acid having 2-5 carbon atoms; providing a second solution including nitric acid, acetic anhydride, and acetic acid; and transferring the first solution and the second solution to a microreactor, obtaining a nitrate ester after a residence time. In particular, the ratio of the weight of nitric acid to the total volume of the acetic anhydride and acetic acid is 1:1 to 1:3.5. The ratio of the molar amount of nitric acid to the hydroxyl group equivalent of the compound is from 1:1 to 15:1.

A method for preparing a nitrate ester is provided. The method includes providing a first solution including a compound (which has at least one hydroxyl group) and a carboxylic acid having 2-5 carbon atoms; providing a second solution including nitric acid, acetic anhydride, and acetic acid; and transferring the first solution and the second solution to a microreactor, obtaining a nitrate ester after a residence time. In particular, the ratio of the weight of nitric acid to the total volume of the acetic anhydride and acetic acid is 1:1 to 1:3.5. The ratio of the molar amount of nitric acid to the hydroxyl group equivalent of the compound is from 1:1 to 15:1.

A method for preparing a nitrate ester is provided. The method includes providing a first solution including a compound (which has at least one hydroxyl group) and a carboxylic acid having 2-5 carbon atoms; providing a second solution including nitric acid, acetic anhydride, and acetic acid; and transferring the first solution and the second solution to a microreactor, obtaining a nitrate ester after a residence time. In particular, the ratio of the weight of nitric acid to the total volume of the acetic anhydride and acetic acid is 1:1 to 1:3.5. The ratio of the molar amount of nitric acid to the hydroxyl group equivalent of the compound is from 1:1 to 15:1.