Synlett 2019; 30(02): 213-217
DOI: 10.1055/s-0037-1611939
letter
© Georg Thieme Verlag Stuttgart · New York

A Convenient Protocol for the Synthesis of Fatty Acid Amides

Silje J. R. Johansson
a   Department of Chemistry, Biology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway   Email: jens.mj.nolsoe@nmbu.no
,
Tonje Johannessen
a   Department of Chemistry, Biology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway   Email: jens.mj.nolsoe@nmbu.no
,
Christiane F. Ellefsen
a   Department of Chemistry, Biology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway   Email: jens.mj.nolsoe@nmbu.no
,
Mali S. Ristun
a   Department of Chemistry, Biology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway   Email: jens.mj.nolsoe@nmbu.no
,
Simen Antonsen
a   Department of Chemistry, Biology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway   Email: jens.mj.nolsoe@nmbu.no
,
a   Department of Chemistry, Biology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway   Email: jens.mj.nolsoe@nmbu.no
b   Department of Pharmaceutical Chemistry, School of Pharmacy, University of Oslo, P.O. Box 1068, Blindern, 0316 Oslo, Norway
,
Yngve Stenstrøm
a   Department of Chemistry, Biology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway   Email: jens.mj.nolsoe@nmbu.no
,
a   Department of Chemistry, Biology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway   Email: jens.mj.nolsoe@nmbu.no
› Author Affiliations
A postdoctoral scholarship for S.A. from the Department of Chemistry, the Norwegian University of Life Sciences, as well as funding from the Research Council of Norway for a research scholarship to J.M.J.N. and grants to Y.S. (NFR 209335 and NFR 244351) are gratefully acknowledged. T.V.H. is grateful for financial support from the Research Council of Norway (FRIPRO-FRINATEK 230470).
Further Information

Publication History

Received: 16 October 2018

Accepted after revision: 21 November 2018

Publication Date:
19 December 2018 (online)


Abstract

Several classes of biologically occurring fatty acid amides have been reported from mammalian and plant sources. Many amides conjugated with fatty acids of mammalian origin exhibit specific activation of individual receptors. Their potential as pharmacological tools or as lead compounds towards the development of novel therapeutics is of great interest. Hence, access to such amides by a practical, high-yielding and scalable protocol without affecting the geometry or position of sensitive functionalities is needed. A protocol that meets all these requirements involves activation of the corresponding acid with carbonyl diimidazole (CDI) followed by reaction with the desired amine or its hydrochloride. More than fifty compounds have been prepared in generally high yields.

Supporting Information

 
  • References and Notes

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  • 21 General Procedure for Amide CouplingTo a stirred solution of the fatty acid (1.0 mmol, 1.0 equiv.) in CH2Cl2 (5 mL) was added CDI (0.178 g, 1.1 mmol, 1.1 equiv.). After 30 min at room temperature, the amine (1.1 mmol, 1.1 equiv.) was added. After 12 h, CH2Cl2 (25 mL) was added, followed by saturated aqueous NH4Cl. The mixture was acidified to pH 2 by addition of HCl, the organic phase was separated, and the aqueous layer was further extracted with CH2Cl2 (3 × 10 mL). The organic phases were combined, dried over Na2SO4, filtered, and concentrated in vacuo, to give the amide.Example 1: (5Z,8Z,11Z,14Z,17Z)-N-[(R)-1-phenylethyl]icosa-5,8,11,14,17-pentaenamide (R-28)Starting with EPA (0.302 g, 1.0 mmol, 1.0 equiv.) and (R)-α-methylbenzylamine (0.133 g, 0.14 mL, 1.1 mmol, 1.1 equiv.). Yield 0.376 g, 93%; TLC (hexane/EtOAc 75:25, visualized by UV and KMnO4 stain): Rf = 0.20; [α]D 20 +5.2 (c = 0.2, MeOH). 1H NMR (400 MHz, CDCl3): δ = 7.49–7.06 (m, 5 H), 5.65 (d, J = 8.2 Hz, 1 H), 5.47–5.27 (m, 10 H), 5.15 (p, J = 7.1 Hz, 1 H), 2.91–2.73 (m, 8 H), 2.18 (dd, J = 8.3, 6.6 Hz, 2 H), 2.15–2.02 (m, 4 H), 1.79–1.67 (m, 2 H), 1.50 (d, J = 6.9 Hz, 3 H), 0.98 (t, J = 7.5 Hz, 3 H). 13C NMR (100 MHz, CDCl3): δ = 171.7, 143.2, 132.0, 129.1, 128.7 (2 × CH), 128.6, 128.5, 128.2, 128.2, 128.1, 128.0, 127.8, 127.3, 126.9, 126.1(2 × CH), 48.6, 36.1, 26.6, 25.6, 25.5, 25.4, 21.6, 20.5, 14.2. IR(ATR): νmax = 3300, 3014, 2964, 1644, 1544 cm–1. HRMS (EI+): exact mass calcd for C28H39NO [M]+ m/z = 405.3032; found: 405.3051.Antipodal S-28Yield 0.403 g, >96%; [α]D 20 –5.4 (c = 0.3, MeOH).Example 2: (4Z,7Z,10Z,13Z,16Z,19Z)-N-[(R)-1-phenylethyl]-docosa-4,7,10,13,16,19-hexaenamide (R-14)Starting with DHA (0.328 g, 1.0 mmol, 1.0 equiv.) and (R)-α-methylbenzylamine (0.133 g, 0.14 mL, 1.1 mmol, 1.1 equiv.). Yield 0.417 g, >96%; TLC (hexane/EtOAc 75:25, visualized by UV and KMnO4 stain): Rf = 0.23; [α]D 20 +6.5 (c = 0.2, MeOH). 1H NMR (400 MHz, CDCl3): δ = 7.39–7.21 (m, 5 H), 5.68 (d, J = 7.9 Hz, 1 H), 5.47–5.26 (m, 12 H), 5.15 (p, J = 7.0 Hz, 1 H), 2.91–2.77 (m, 10 H), 2.46–2.38 (m, 2 H), 2.27–2.21 (m, 2 H), 2.13–2.03 (m, 2 H), 1.49 (d, J = 7.0 Hz, 3 H), 0.98 (t, J = 7.5 Hz, 3 H). 13C NMR (100 MHz, CDCl3): δ = 171.2, 143.1, 132.0, 129.3, 128.6 (2 × CH), 128.5, 128.2 (2 × CH), 128.2 (2 × CH), 128.1, 128.0, 128.0, 127.8, 127.3, 127.0, 126.2 (2 × CH), 48.6, 36.5, 25.6, 25.6, 25.6, 25.5, 23.4, 21.7, 20.5, 14.2. IR(ATR): νmax = 3294, 3014, 2964, 1644, 1544 cm–1. HRMS (EI+): exact mass calcd for C30H41NO [M]+ m/z = 431.3188; found: 431.3164.Antipodal S-14Yield 0.430 g, >96%; [α]D 20 –6.2 (c = 0.2, MeOH).Example 3: (5Z,8Z,11Z,14Z,17Z)-icosa-5,8,11,14,17-pentaen morpholide (12)Starting with EPA (0.302 g, 1.0 mmol, 1.0 equiv.) and morpholine (0.096 g, 0.095 mL, 1.1 mmol, 1.1 equiv.). Yield 0.417 g, >96%; TLC (hexane/EtOAc 40:60, visualized by UV and KMnO4 stain): Rf = 0.32. 1H NMR (400 MHz, CDCl3): δ = 5.45–5.25 (m, 10 H), 3.66 (dd, J = 5.7, 3.9 Hz, 4 H), 3.62 (d, J = 4.9 Hz, 2 H), 3.45 (d, J = 4.9 Hz, 2 H), 2.90–2.75 (m, 8 H), 2.34–2.28 (m, 2 H), 2.18–2.02 (m, 4 H), 1.72 (p, J = 7.5 Hz, 2 H), 0.98 (t, J = 7.5 Hz, 3 H). 13C NMR (100 MHz, CDCl3): δ = 171.5, 132.0, 129.2, 128.7, 128.5, 128.2, 128.2, 128.1, 128.0, 127.8, 126.9, 66.9, 66.6, 45.9, 41.8, 32.3, 26.7, 25.6, 25.6, 25.5, 24.9, 20.5, 14.2. IR (ATR): νmax = 3009, 2964, 2931, 2863, 1656, 1432 cm–1. HRMS (EI+): exact mass calcd for C24H37NO2 [M]+ m/z = 371.2824; found: 371.2833.
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