N-(2-Oxo-3-oxetanyl)carbamic Acid Esters as N-Acylethanolamine Acid Amidase Inhibitors: Synthesis and Structure–Activity and Structure–Property Relationships

Abstract

The β-lactone ring of N-(2-oxo-3-oxetanyl)amides, a class of N-acylethanolamine acid amidase (NAAA) inhibitors endowed with anti-inflammatory properties, is responsible for both NAAA inhibition and low compound stability. Here, we investigate the structure−activity and structure−property relationships for a set of known and new β-lactone derivatives, focusing on the new class of N-(2-oxo-3-oxetanyl)carbamates. Replacement of the amide group with a carbamate one led to different stereoselectivity for NAAA inhibition and higher intrinsic stability, because of the reduced level of intramolecular attack at the lactone ring. The introduction of a syn methyl at the β-position of the lactone further improved chemical stability. A tert-butyl substituent in the side chain reduced the reactivity with bovine serum albumin. (2S,3R)-2-Methyl-4-oxo-3-oxetanylcarbamic acid 5-phenylpentyl ester (27, URB913/ARN077) inhibited NAAA with good in vitro potency (IC 50 = 127 nM) and showed improved stability. It is rapidly cleaved in plasma, which supports its use for topical applications.

Synthesis and Structure–Activity Relationship (SAR) of 2-Methyl-4-oxo-3-oxetanylcarbamic Acid Esters, a Class of Potent N-Acylethanolamine Acid Amidase (NAAA) Inhibitors

“…24 The (S)-configuration at position 3 in the β-lactone ring of 2 is essential for inhibitory potency, as indicated by the substantially lower activity of its enantiomer, (R)-OOPP (IC 50 = 6.0 μM). 24 The benzyl carbamate 1 was less potent than 2 at inhibiting NAAA (IC 50 = 2.96 μM), 28 whereas its enantiomer, (R)-2-oxo-3-oxetanylbenzyl carbamate, showed potency comparable to that of 2 (IC 50 = 0.70 μM). 28 This indicated an opposite stereochemical preference of NAAA at position 3 of the β-lactone ring in the carbamic acid ester series relative to the amide series.…”

“…24 The benzyl carbamate 1 was less potent than 2 at inhibiting NAAA (IC 50 = 2.96 μM), 28 whereas its enantiomer, (R)-2-oxo-3-oxetanylbenzyl carbamate, showed potency comparable to that of 2 (IC 50 = 0.70 μM). 28 This indicated an opposite stereochemical preference of NAAA at position 3 of the β-lactone ring in the carbamic acid ester series relative to the amide series. The introduction of a methyl group with (S)-stereochemistry at the β-position of the β-lactone ring of (R)-2-oxo-3-oxetanylbenzyl carbamate led to the corresponding threonine-derived β-lactone analogue that, although slightly less potent (IC 50 = 1.0 μM), 28 showed an increased chemical stability with respect to serine-derived β-lactone analogues.…”

“…Experimental procedure and NMR are according to the literature. 28,37 General Procedure I for the Synthesis of Carbamates 14b,e,h (Scheme 4). Preparation of β-Hydroxycarboxylic Acids 15b,e,h (Step 1).…”

Therapeutic Potential of Fatty Acid Amide Hydrolase, Monoacylglycerol Lipase, and N-Acylethanolamine Acid Amidase Inhibitors

“…In fact, most amide-based β-lactone derivatives were rapidly hydrolyzed in aqueous buffer at pH 7.4 with half-lives of less than 20 minutes, whereas the β-substituted methyl group endowed the β-lactone derivatives with improved stability (half-life > 70 min). 133 Afterwards, urea-and carbamate-based β-lactone derivatives were identified to possess drastically increased chemical stability at both pH 5 and pH 7.4 in comparison with the corresponding amide-based β-lactone derivatives. 133 Structure-activity relationships revealed that the (R)-configuration of carbamate-based β-lactones was favorable for inhibitory capacity, whereas the (S)-configuration is suitable for urea-based β-lactones ( Figure 40).…”

Synthesis, Biological Evaluation, and 3D QSAR Study of 2-Methyl-4-oxo-3-oxetanylcarbamic Acid Esters as N-Acylethanolamine Acid Amidase (NAAA) Inhibitors

“…32 Structure−activity relationship (SAR) studies of α-amino-β-lactone derivatives, as carbamic acid esters, investigated the effects on NAAA inhibition of side chain modifications and the stereochemical requirements of the introduction of a β-substitution. 33−35 These works led to the identification of compounds that were highly potent at inhibiting both rat and human NAAA, such as β-lactones 1 (ARN077) 33,34,36 and 2…”