Analogues of platelet activating factor. 8. Antagonists of PAF containing an aromatic ring linked to a pyridinium ring.

A series of platelet activating factor (PAF) antagonists containing a quaternary pyridinium ring connected through an amide, imide, or carbamate linkage to a substituted aromatic ring was prepared. Of these compounds, those containing a branched imide linkage of the form (CON-(COCH3)CH2, 37-51, and 59) generally showed excellent PAF antagonist properties in vitro. Structure-activity relationships within this series of compounds were studied extensively with respect to substituents and the position of substitution in both the aromatic and pyridinium rings. Several of these compounds (40 and 44) showed in vitro PAF antagonism at less than 0.1 microM and are as potent as CV-6209, the most potent PAF antagonist reported in the literature. Less active PAF antagonists were those bearing simple amide linkages (20-23, 27-29, and 31-35), linear imide linkages (62-63), or carbamate linkages (66 and 68), between the two aromatic rings. A number of our PAF antagonists were tested in vivo in mice and rabbits for their ability to protect these animals against a lethal injection of PAF. Those antagonists that are particularly potent (IC50 < 0.1 microM) provide excellent protection against an LD97 dose of PAF in rabbits. The relationships between structure and activity in vitro and in vivo are presented and compared to literature standards.

Analogues of platelet activating factor. 7. Bis-aryl amide and bis-aryl urea receptor antagonists of PAF.

A series of bis-aryl amide (13-57 and 66-81) and bis-aryl urea (58 and 85) antagonists of platelet-activating factor (PAF) was prepared that contain, separating the two aromatic rings, linear amide linkages of the form -(CH2)nCONH- (n = 0-2), -OCH2CONH-, and -(CH2)nNHCO- (n = 0-1), branched amide linkages of the form -(CH2)nN(COR)- (n = 1-3, R = CH3 or n-C3H7), and -N(COCH3)CH2-, and urea linkages of the form -NHCONH- and -CH2N(CONHCH3)-. These compounds were examined for their ability to inhibit PAF-induced platelet aggregation of rabbit platelets. These in vitro data were compared to similar data obtained for a number of known PAF antagonists. The compounds were evaluated in vivo, in the mouse, for their ability to prevent death induced by a lethal challenge of PAF. The relationships between the biological activity and the nature, lipophilicity, and position of substituents of the aromatic rings were studied. Best activity was observed for compounds having linkages of the type -CH2CONH-, -CH2N(COR)-, and -CH2NHCO-. Many of these compounds inhibit PAF-induced platelet aggregation with IC50's under 1 microM.

Studies of the effect of a platelet-activating factor antagonist, CL 184,005, in animal models of gram-negative bacterial sepsis.

The effect of CL 184,005, a potent and specific platelet-activating factor antagonist, has been examined in a variety of animal models relevant to gram-negative bacterial sepsis. Pretreatment of mice with CL 184,005 protected them from the lethal effects of platelet-activating factor. When rats or primates rendered hypotensive with endotoxin were treated with CL 184,005, blood pressure was normalized. Pretreatment of rats with CL 184,005 protected them from the gastrointestinal lesions induced by endotoxin. Pretreatment of rats and mice with CL 184,005 protected them from the lethal effects of endotoxin. Plasma tumor necrosis factor levels in endotoxin-treated mice were lower when the mice were pretreated with CL 184,005. These observations suggest that CL 184,005 may be potentially useful in the treatment of gram-negative bacterial sepsis, and the agent is undergoing clinical evaluation.

Analogues of platelet activating factor. 6. Mono- and bis-aryl phosphate antagonists of platelet activating factor.

A series of aryl phosphoglyceride (3, 19-61) and bis-aryl phosphate (67-135) antagonists of platelet activating factor (PAF) were prepared. A group of four bifunctional phosphorus reagents (5a-c and 7) were developed that allowed the preparation of these aryl phosphates in which the position of aromatic substitution can be varied. These compounds were examined for their ability to inhibit PAF-induced platelet aggregation of rabbit platelets. Selected compounds were also evaluated for their ability to displace [3H]PAF from its receptor on rabbit platelets. These in vitro data were compared to similar data obtained for a number of known PAF antagonists. The compounds were evaluated in vivo, in both the mouse and rabbit, for their ability to prevent death induced by a lethal challenge of PAF. The relationships between the biological activity and the nature, lipophilicity, and position of substituents of the aromatic rings were studied. Compound 105 (CL 184005) has been selected to undergo further development as a potential therapeutic agent for the treatment of septic shock in man.

Analogues of platelet activating factor. 4. Some modifications of the phosphocholine moiety.

Racemic analogues of platelet activating factor (PAF) in which the methylene bridge separating the phosphate and trimethylammonium moieties is altered in length (7a-f) have been prepared. Increasing the length of this bridge results in a progressive decrease in the hypotensive and platelet aggregation responses. Analogues in which the phosphocholine group is substituted with a methyl group (7h and 7i) or a phenyl group (5j) or in which the methylene bridge is replaced with a meta-substituted benzyl group (5k) have been prepared. With respect to both the blood pressure and platelet aggregation responses, 7i and 5k showed little if any changes in potency compared to racemic C16-PAF (1a). While 7h is more potent than 1a with respect to both the hypotensive and platelet aggregation properties, 5j is less potent. Replacement of the phosphate moiety of C18-PAF (1b) with a phosphonate group (7g) leads to decreased activity in both assays. Analogue 11, in which the phosphocholine group has been replaced with a 4-(trimethylammonio)butoxy group, exhibited no detectable hypotensive or platelet aggregating activity. None of the analogues exhibited a separation of the blood pressure and platelet aggregation activities.

Analogues of platelet activating factor (PAF). 2. Some modifications of the glycerine backbone.

Racemic analogues of platelet activating factor (PAF) that contain a methylene group between the C2 and C3 carbon atoms (39) or between the C1 and C2 carbon atoms (40) have been synthesized. These compounds show reduced platelet aggregation and hypotensive activity as measured against racemic C16 PAF. Compounds in which the C1 carbon atom of PAF is substituted with one or two methyl groups (41 and 42, respectively) or the C3 carbon is substituted with a single methyl group (43) have been synthesized. Platelet aggregation and hypotensive responses produced by these compounds are significantly less than those obtained with racemic C16 PAF. None of the above compounds exhibit a separation of the platelet aggregation and hypotensive activities.

Analogues of platelet activating factor (PAF). 1. Some modifications of the alkoxy chain.

Analogues of platelet activating factor (PAF) in which the ether oxygen has been removed (6) and in which the alkoxy chain at C1 has been replaced with a o-, p-, or m-alkylphenoxy group (30, 31, and 35, respectively) have been prepared. Compound 6 shows reduced platelet aggregation and hypotensive activity in comparison with C16 and C18 PAF. The results obtained for compounds 30, 31, and 35 indicate that the hypotensive and platelet aggregating responses are sensitive to structural modification of the ether chain. The ortho analogue 30 shows no platelet aggregating activity and only a weak hypotensive response. The para analogue 31 exhibits a moderate decrease in activity in both assays. The meta analogue 35 is the most active of the three.

Prostaglandins and congeners. 22. Synthesis of 11-substituted derivatives of 11-deoxyprostaglandins E1 and E2. Potential bronchodilators.

The interesting bronchodilator activity of l-11-deoxy-11 alpha-[(2-hydroxyethyl)thio]prostaglandin E2 methyl ester (3a) is described. The preparation of 3a and its analogues by Michael-type additions to various members of the PGA series or by total synthesis using the lithiocuprate conjugate addition process is also described. Structure-activity relationships in this series are discussed.

Prostaglandins and congeners. 15. Synthesis and bronchodilator activity of dl-11-deoxy-15- or 16-alkylprostaglandins.

The synthesis of dl-11-doxy-15- or 16-alkylprostaglandins by the conjugate addition of appropriately substituted lithium alanate or lithium cuprate reagents to several cyclopentenones is described as is the preparation of the requisite intermediate (E)-1-iodo-1-alkenyl compounds 4, 22, 23, and 31. The bronchodilator activity of these prostaglandin congeners is presented.

Prostaglandins and congeners. 16. Synthesis and bronchodilator activity of dl-11-doexy-3-thiaprostaglandins.

The interesting bronchodilator activity of certain dl-11-deoxy-3-thiaprostaglandins and their preparation by the conjugate addition of appropriately substituted (E)-1-alkenyllithio cuprate reagents to requisite cyclopentenones are described.

Prostaglandins and congeners. 14. Synthesis and bronchodilator activity of dl-16,16-trimethyleneprostaglandins.

The interesting bronchodilator activity of novel dl-16,16-trimethyleneprostaglandin congeners and their preparation via the conjugate addition of the appropriate vinyl lithiocuprate reagent to several cyclopentenones are described. Also discussed is the preparation of the key intermediate vinyl iodine 7.

Prostaglandins and congeners. IX. The synthesis of 15-deoxy-16-, 17-, or 20-hydroxyprostaglandins and 15-deoxy-15-hydroxymethylprostaglandin E2.

Prostaglandin congeners wherein the 15-hydroxy group is moved to the C16, C17, or C20 position or is replaced by a hydroxymethyl group were prepared via the 1, 4-addition of a lithium trialkyl-trans-alkenyl alanate to an appropriate cyclopentenone. Several of the 16-hydroxy derivatives showed significant activity as constrictors of the isolated gerbil colon and in bronchodilator and anti-secretory assays.