TITLE: Synthesis of 1-(3-chlorophenethyl)-3-cyclopentylpyrimidine-2,4,6-(1H,3H,5H)-trione (CP8)
AUTHORS: Carole JR Bataille, Katherine Brimblecombe, Stephanie J Cragg

[DESCRIPTION]
A structure-activity relationship-based modification of pyrimidine-2,4,6-triones led to 1-(3-chlorophenethyl)-3-cyclopentylpyrimidine-2,4,6-(1H,3H,5H)-trione (CP8), a potent and highly selective CaV1.3 L-type calcium channel antagonist. This protocol is an adaption of Kang, S., Cooper, G., Dunne, S. et al., 2012's method of the synthesis of this chemical.

[GUIDELINES]
All solvents and reagents were used as supplied (analytical or HPLC grade) without prior purification. Water was purified by an Elix® UV-10 system. In vacuo refers to the use of a rotary evaporator attached to a diaphragm pump. 

Thin layer chromatography was performed on aluminium plates coated with 60 F254 silica.

Plates were visualised using UV light (254 nm) or 1% aq. KMnO4. Flash column chromatography was performed on Kieselgel 60M silica in a glass column. 

Nuclear magnetic resonance (NMR) spectra were recorded on Bruker Avance spectrometers (AVIII 400) in the deuterated solvent stated. The field was locked by external referencing to the relevant deuteron resonance. Chemical shifts (d) are reported in parts per million (ppm) referenced to the solvent peak. 1H spectra reported to two decimal places (see Figure 2), and 13C spectra reported to one decimal place (see Figure 3), and coupling constants (J) are quoted in Hz (reported to one decimal place). 

 Low-resolution mass spectra were recorded on an Agilent 6120 spectrometer from solutions of MeOH.  


 


 



[STEPS]
SECTION: Synthesis of 1-(3-chlorophenethyl)-3-cyclopentylpyrimidine-2,4,6-(1H,3H,5H)-trione (CP8)
1. Add 357 µL 2-(3-chlorophenyl)ethylamine (2.58 mmol, 1.0 eq.) to a solution of 290 mg of Cyclopentaneisocyanate (2.58 mmol, 1.0 eq.) in 10 mL of dichloromethane.
SECTION: Synthesis of 1-(3-chlorophenethyl)-3-cyclopentylpyrimidine-2,4,6-(1H,3H,5H)-trione (CP8)
2. Stir at RT for 5 h.
SECTION: Synthesis of 1-(3-chlorophenethyl)-3-cyclopentylpyrimidine-2,4,6-(1H,3H,5H)-trione (CP8)
3. Monitor completion with Low-Resolution Mass Spectrometry.
SECTION: Synthesis of 1-(3-chlorophenethyl)-3-cyclopentylpyrimidine-2,4,6-(1H,3H,5H)-trione (CP8)
4. Add 276 µL Malonyl chloride (2.84 mmol, 1.1 eq.)  dropwise under vigorous stirring over 5 min. 
SECTION: Synthesis of 1-(3-chlorophenethyl)-3-cyclopentylpyrimidine-2,4,6-(1H,3H,5H)-trione (CP8)
5. Stir mixture for 1 h and concentrate in vacuo.
SECTION: Synthesis of 1-(3-chlorophenethyl)-3-cyclopentylpyrimidine-2,4,6-(1H,3H,5H)-trione (CP8)
6. Purify residue by column chromatography on silica gel (EtOAc/pentane, 1:4), product should be a white solid (687 mg, 80%)
SECTION: Nuclear Magnetic Resonance (NMR) Spectroscopy
7. Check data from NMR spectroscopy is comparable with the literature (Kang, S., Cooper, G., Dunne, S. et al., 2012):

1H NMR (400 MHz, CDCl3) δ 7.25 – 7.19 (m, 3H), 7.13 (dt, J = 6.7, 2.1 Hz, 1H), 5.20 – 5.07 (m, 1H), 4.13 – 4.03 (m, 2H), 3.62 (s, 2H), 2.92 – 2.84 (m, 2H), 1.94 (tqd, J = 8.0, 4.9, 2.0 Hz, 4H), 1.89 – 1.79 (m, 2H), 1.61 – 1.57 (m, 2H)

13C NMR (101 MHz, CDCl3) δ 164.9, 164.6, 151.1, 140.0, 134.5, 123.0, 129.2, 127.3, 127.1, 54.6, 42.8, 40.3, 33.8, 28.8, 25.7; LRMS m/z (ESI¯) 333.1 [M-H]¯