EASY NMR

 Benzyl 2-{[1-(chlorocarbonyl)cyclopentyl]methyl}entanoate

Oxalyl chloride (1.15 ml, 13.2 mmol) was added to an ice-cooled solution of 1-{2-[(benzyloxy)carbonyl]pentyl}cyclopentanecarboxylic acid (EP 274234, Example 16) (2.0 g, 6.3 mmol) in dry dichloromethane (20 ml), and the solution stirred at room temperature for 2 hours. The reaction mixture was concentrated under reduced pressure and the residue azeotroped with dichloromethane (3×), to give the title compound as a golden oil, 2.1 g; 

¹H NMR (CDCl₃, 300 MHz) δ: 0.88 (t, 3H), 1.28 (m, 2H), 1.43 (m, 2H), 1.63 (m, 6H), 2.00 (m, 1H), 2.08-2.35 (m, 3H), 2.44 (m, 1H), 5.15 (s, 2H), 7.28 (m, 5H).