Tryptase inhibitor

Af-(ter -Butoxycarbonyl)-3-hydroxymethylpiperidine is a building block in the synthesis of a potent tryptase inhibitor. It is produced by stereospecific esterification of the racemic alcohol with succinic anhydride [30]. The enzymatic resolution is followed up by separation of... 

A number of 1-substituted 2(l//)-pyrazinone derivatives show antithrombotic activity as selective inhibitors of the tissue Factor Vila complex <2003BML23I9> and were examined as mast cell tryptase inhibitors <2004BML48I9>. As a curious effect, dihydropyrazines proved to show DNA strand-breakage activity <2005CPB1359>. 

The Synthesis of S-N(tert-Butoxycarbonyl)-3-Hydroxymethylpiperidine (Tryptase Inhibitor)... 

S)-N-(tert-butoxycarbonyl)-hydroxymethylpiperidine (8) is a key intermediate in the synthesis of a potent tryptase inhibitor (Scheme 7.5). It was synthesized from (R,.S)-3-hydroxyrnethylpiperidine via fractional crystallization of the corresponding L(-)dibenzoyl tartrate salt followed by hydrolysis and acylation [17]. The lipase from Pseudomonas cepacia (PS-30) immobilized on polypropylene accurel PP catalyzed the esterification of racemic 6 with succinic anhydride and toluene, giving the (S)-hemisuccinate ester (7). This was easily separated and hydrolyzed by base to the (S)-Boc-protected 3-hydroxymethylpiperidine (8). Using this repeated esterification procedure gave a 32% yield (maximum theoretical yield = 50%) and 98.9% . 

The synthesis of an enantiopure p-lactam as advanced precursor of thrombin and tryptase inhibitor, has been centered on the condensation between 5-2-pyridylthio 5-(4-methoxyphenoxy)pentanoate and the AM-methoxyphenylimine derived from 0,0-cyclohexylidene D-glyceraldehyde (Scheme 23), [84]. 

Scheme 23 Synthesis of an enantiopure P-lactam as precursor of thrombin and tryptase inhibitor...

A series of piperidine containing All activated C4-carboxy azetidinone tryptase inhibitors was prepared by Sutton et al. [213] adopting solid-phase technology. Wang resin was used to attach with the carboxyl group of the (5-lactam moiety and removal from the resin surface was achieved as usually by 20% TFA in CH2C12. 

Scheme 53 Preparation of N1 activated C4-carboxy azetidinone tryptase inhibitors using Wang...

In addition to the use in the synthesis of potential hepatitis C drugs, microwave-assisted chemistry has also been used in the synthesis of mast cell tryptase inhibitors, thrombin inhibitors, and Factor Xa inhibitors. The trypsin-like serine protease tryptase is the major secretory product of human mast cells and has been implicated as an inflammatory mediator in a number of conditions, especially asthma. Once released upon mast cell activation, the tryptase cleaves substrates that otherwise cause smooth muscle relaxation and thereby bronchi- and vasodilation. It is therefore not surprising that numerous reports on low molecular weight tryptase inhibitors have appeared. 

Recently, the synthesis and evaluation of a new pyrazinone class of tryptase inhibitors has been reported. One step in the preparation of these compounds involved regioselective chloride displacements from a dichloropyrazinone scaffold using amines and anilines as nucleophiles. The aniline reactions required the use of microwave-assisted heating for 12 min at 120 °C, as illustrated in Scheme 23 [84]. Although the aniline-derived compounds (e.g., 50) were modest inhibitors, other compounds from this study, synthesized by classical heating methods, were shown to be highly potent tryptase inhibitors. 

Scheme 23 Microwave-accelerated nucleophilic substitution in tryptase inhibitor synthesis...

The monofunctional tryptase inhibitor APC-366 (Axys Pharmaceuticals) reduces the acute airway response and histamine release to allergen in a pig model of allergen-induced asthma [19]. APC-366 is also effective in a sheep model of allergen-induced asthma but was only poorly effective in asthma patients (proof-of-principle) [8], The compound was in clinical development phase II for asthma (inhalative). Although highly selective for tryptase over plasmin and plasma kal-likrein, APC-366 was not selective against thrombin and trypsin [13], Another monofunctional tryptase inhibitor is bis(5-amidino-2-benzimidazol-yl)methane (BABIM) which has been shown to be effective in the sheep. Further development of the compound was, however, discontinued, maybe because of the lack of selectivity over trypsin [13, 16, 17] (Figure 3.2.2). 

Because of their high selectivity against other serine proteases, for example thrombin, trypsin, or factor Xa, the development of bifunctional tryptase inhibitors has attracted much attention during recent years. Several classes of effective dibasic tryptase inhibitor have been reported, recently [13,14, 23], Herein, we describe syn-... 

Fig. 3.2.2. Two monofunctional tryptase inhibitors for inhalative application - APC 366 (Axys Pharmaceuticals) and BABIM.

The in-vitro inhibition activity of the synthesized target compounds against human mast cell tryptase is summarized in Tables 3.2.1 and 3.2.2 Compound 8, which contains aminomethyl benzyl moieties as head groups, was the most potent of the pyran series (type I), with a Ki value of 1.3 nM. Compared with 8, the tryptase inhibitors with aminomethylcyclohexyl substituents (17, 18, and 21), were 100-fold (Ki = 130 nM), 60-fold (Ki = 75 nM), and approximately 90-fold (Ki = 120 nM) less... 

We have created efficient syntheses of remarkably potent and selective bifunctional tryptase inhibitors, which are also competitive and reversible, containing pyran moieties and hetero and non-hetero aryl diynes as scaffolds. Several modifications at the core templates and the linker moieties are well tolerated without significant loss of inhibition activity. In contrast with previous results published recently [32], it was also apparent from the aryl diyne inhibitors that the distance between the two terminal amino groups can be considerably less than 30 bonds in highly potent target compounds (e.g. 9 and 29 with 26 bonds each). The in-vitro potencies of the compounds were between 1 im for 26 and 1.3 nM for 15 with high selectivity against other serine proteases (trypsin, thrombin, and factor Xa, respectively) in... 

The Bristol-Meyers Squibb company wanted the simple heterocycle 8 for the preparation of a tryptase inhibitor. As 8 is an amine, tartaric acid was the first choice for a resolving agent. It again turned out that a modified version of the first choice was the best. Tartaric acid is so good at resolutions that simple variations, such as the dibenzoate ester 9, often work well. 

Fig. 2.9 Chemical structure of the bivalent human y -tryptase inhibitor CRA-2059 (13) [80].

The strong effect of the mode of presentation of the binding heads and the critical length of the spacer for y tryptase inhibitors was well evidenced by a distance scan of the A/D and B/C subunits of y -tryptase... 

S)-A(tert-butoxycarbonyl)-3-hydroxymethylpiperidine 56 (Figure 16.15) is a key intermediate in the synthesis of a potent tryptase inhibitor 57 [87]. (S)-56 was made by lipase PS-30 (Pseudomonas cepflda)-catalyzed resolution of 7 ,5-N-(tert-butoxycarbonyl)-3-hydroxymethylpiperidine 56. (S)-56 was obtained at a 16% yield... 

FIGURE 16.15 Tryptase inhibitors . Enzymatic preparation of (S )-A -(tert-butoxycarbonyl)-3-hydroxymethyl piperidine 56. 

A typical recent example comes from some work on tryptase inhibitors, tryptase being a serine protease of interest for the treatment of asthma. Compound 44, shown in Figure 8.2, was found to be a 2.5 nM inhibitor of human tryptase, but a 365 nM inhibitor of the mouse enzyme, and a 400 nM inhibitor of monkey tryptase. Larger species specificity effects than this have been observed for some renin inhibitors, including zankiren (Figure 8.2) and the... 

Figure 8.2 Structures of the tryptase inhibitor, Compound 44 (Palmer, J.T., et al. Design and synthesis of selective keto-l,2,4-oxadiazole-based tryptase inhibitors. Bioorg. Med. Chem. Lett. 2006, 16, 3434-3439.) and the renin inhibitors aliskiren and zankiren.

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