A process for the preparation of hexanoic acid, 6-(nitrooxy)-, -3-[ -2-[ -7-(ethylamino)-7-oxo-2-hepten-1-yl]-3,5-dihydroxycyclopentyl]-1-(2-phenylethyl)-2-propen-1-yl ester of formula (I): said process comprising the following steps: 1) reacting compound (II): with 6-(nitrooxy)hexanoyl chloride (IVa) in the presence of 4-dimethylaminopyridine in free form, to obtain the compound (III) 2) removing the boronate protective group of the compound (III) to obtain compound of formula (I); 3) purification of the compound (I); said process is characterized in that the 6-(nitrooxy)hexanoyl chloride (IVa) is prepared by a process comprising the following steps: 4) reacting the 2-caprolactone (V) with an inorganic base selected from KOH, NaOH and LiOH to obtain 6-hydroxyhexanoic acid salt of formula (VI) wherein M is K, Na or Li; 5) nitrating a compound of formula (VI) with a mixture of HNO 3 and H 2 SO 4 to obtain the 6-(nitrooxy)hexanoic acid (VIIa); 6) purifying the nitration mixture by reverse phase chromatography using formic acid in water (H 2 O+HCOOH) and acetonitrile as eluent to obtain pure 6-(nitrooxy)hexanoic acid of formula (Villa) having a content of 6-{[6-(nitrooxy)hexanoyl]oxy} hexanoic acid of formula (VIIb) below the HPLC detection limit (<0.05%); and 7) reacting the pure 6-(nitrooxy)hexanoic acid (VIIa) with a chlorinating agent to obtain 6-(nitrooxy)hexanoyl chloride (IVa). 1) reacting compound (II): with 6-(nitrooxy)hexanoyl chloride (IVa) in the presence of 4-dimethylaminopyridine in free form, to obtain the compound (III) 2) removing the boronate protective group of the compound (III) to obtain compound of formula (I); 3) purification of the compound (I); said process is characterized in that the 6-(nitrooxy)hexanoyl chloride (IVa) is prepared by a process comprising the following steps: 4) reacting the 2-caprolactone (V) with an inorganic base selected from KOH, NaOH and LiOH to obtain 6-hydroxyhexanoic acid salt of formula (VI) wherein M is K, Na or Li; 5) nitrating a compound of formula (VI) with a mixture of HNO 3 and H 2 SO 4 to obtain the 6-(nitrooxy)hexanoic acid (VIIa); 6) purifying the nitration mixture by reverse phase chromatography using formic acid in water (H 2 O+HCOOH) and acetonitrile as eluent to obtain pure 6-(nitrooxy)hexanoic acid of formula (Villa) having a content of 6-{[6-(nitrooxy)hexanoyl]oxy} hexanoic acid of formula (VIIb) below the HPLC detection limit (<0.05%); and 7) reacting the pure 6-(nitrooxy)hexanoic acid (VIIa) with a chlorinating agent to obtain 6-(nitrooxy)hexanoyl chloride (IVa). 4) reacting the 2-caprolactone (V) with an inorganic base selected from KOH, NaOH and LiOH to obtain 6-hydroxyhexanoic acid salt of formula (VI) wherein M is K, Na or Li; 5) nitrating a compound of formula (VI) with a mixture of HNO 3 and H 2 SO 4 to obtain the 6-(nitrooxy)hexanoic acid (VIIa); 6) purifying the nitration mixture by reverse phase chromatography using formic acid in water (H 2 O+HCOOH) and acetonitrile as eluent to obtain pure 6-(nitrooxy)hexanoic acid of formula (Villa) having a content of 6-{[6-(nitrooxy)hexanoyl]oxy} hexanoic acid of formula (VIIb) below the HPLC detection limit (<0.05%); and 7) reacting the pure 6-(nitrooxy)hexanoic acid (VIIa) with a chlorinating agent to obtain 6-(nitrooxy)hexanoyl chloride (IVa). <EOS>