Synthesis and SAR of new 5-phenyl-3-ureido-1,5-benzodiazepines as cholecystokinin-B receptor antagonists

A series of 5-phenyl-3-ureidobenzodiazepine-2,4-diones was synthesized and evaluated as cholecystokinin-B (CCK-B) receptor antagonists. Structure-activity relationship (SAR) studies revealed the importance of the N-1 substituent for potent and selective CCK-B affinity. Addition of substituents at the urea side chain provided in some cases more potent compounds. Moreover the introduction of bulky substituents such as adamantylmethyl at N-1 and resolution of the racemic ureas resulted in our lead compound GV150013.

Thrombin inhibitors based on [5,5] trans-fused indane lactams

A series of trans-fused lactams containing the indane nucleus has been prepared. Compound 19 has much enhanced plasma stability compared with its lactone counterpart and shows appreciable in vitro anticoagulant activity.

Synthetic [5,5] trans-fused indane lactones as inhibitors of thrombin

Synthesis of trans-fused lactones containing the indane nucleus has resulted in a series of potent acylating inhibitors of thrombin. As an example compound 11e has an apparent second order rate constant of 11 x 10(6) M(-1)sec(-1) for the inhibition of thrombin. The anticoagulant activity of these compounds is discussed.

Actual vs perceived EMS response time

OBJECTIVE

To compare patients' perceptions of ambulance response times with the actual ambulance response times to aid quality assurance efforts in EMS management.

METHODS

A convenience sample of patients presenting to an urban ED via EMS were asked a series of four questions pertaining to response time, scene time, time to definitive care, and their expectations of response time. These times were then compared with actual times from the EMS dispatch center. Times were analyzed using multivariate analysis of variance (MANOVA) followed by discriminant analysis.

RESULTS

There was a significant difference between the perceived and actual times for all three questions, by both multivariate analysis and univariate analysis (p < 0.0001). Patients tended to overestimate the actual response times (12.4 min vs 9.1 min) but underestimate the on-scene times (9.1 min vs 12.4 min) and times to definitive care (29.4 min vs 35.0 min).

CONCLUSION

Patients are inaccurate in their estimations of time. Response times are generally overestimated, while scene times and times to definitive care are underestimated. Actual response times often meet patients' expectations (mean 10.8 min), although the patients may not perceive that they have.

5,5-trans lactone-containing inhibitors of serine proteases: identification of a novel, acylating thrombin inhibitor

Synthesis of a variety of 5,5-trans fused lactones, related to compounds found in extracts of Lantana camara, has provided a series of novel acylating inhibitors of human thrombin, trypsin, chymotrypsin and human leucocyte elastase. The most effective thrombin inhibitor is 7 with an IC50 of 130 nM and a Kobs/[1] of 4,000 M-1 s-1.

Novel natural product 5,5-trans-lactone inhibitors of human alpha-thrombin: mechanism of action and structural studies

High-throughput screening of methanolic extracts from the leaves of the plant Lantana camara identified potent inhibitors of human alpha-thrombin, which were shown to be 5,5-trans-fused cyclic lactone euphane triterpenes [O'Neill et al. (1998) J. Nat. Prod. (submitted for publication)]. Proflavin displacement studies showed the inhibitors to bind at the active site of alpha-thrombin and alpha-chymotrypsin. Kinetic analysis of alpha-thrombin showed tight-binding reversible competitive inhibition by both compounds, named GR133487 and GR133686, with respective kon values at pH 8.4 of 1.7 x 10(6) s-1 M-1 and 4.6 x 10(6) s-1 M-1. Electrospray ionization mass spectrometry of thrombin/inhibitor complexes showed the tight-bound species to be covalently attached, suggesting acyl-enzyme formation by reaction of the active-site Ser195 with the trans-lactone carbonyl. X-ray crystal structures of alpha-thrombin/GR133686 (3.0 A resolution) and alpha-thrombin/GR133487 (2.2 A resolution) complexes showed continuous electron density between Ser195 and the ring-opened lactone carbonyl, demonstrating acyl-enzyme formation. Turnover of inhibitor by alpha-thrombin was negligible and mass spectrometry of isolated complexes showed that reversal of inhibition occurs by reformation of the trans-lactone from the acyl-enzyme. The catalytic triad appears undisrupted and the inhibitor carbonyl occupies the oxyanion hole, suggesting the observed lack of turnover is due to exclusion of water for deacylation. The acyl-enzyme inhibitor hydroxyl is properly positioned for nucleophilic attack on the ester carbonyl and therefore relactonization; furthermore, the higher resolution structure of alpha-thrombin/GR133487 shows this hydroxyl to be effectively superimposable with the recently proposed deacylating water for peptide substrate hydrolysis [Wilmouth, R. C., et al. (1997) Nat. Struct.Biol. 4, 456-462], suggesting the alpha-thrombin/GR133487 complex may be a good model for this reaction.

The Role of the Substituent Pattern in Determining Selectivity in the Preparation of Tricarbonyl(η5-cyclohexadienyl)iron(1+) Salts by Acid-Catalyzed Demethoxylation

The factors that determine the selectivity of the acid-catalysed dealkoxylation of unsymmetrically substituted tricarbonyl(η4-alkoxycyclohexa-1,3-diene)iron(0) complexes have been investigated. Regioselective demethoxylation of complexes with a variety of substitution patterns has indicated that the selectivity arises from differences in the stabilization of the reaction intermediates and transition states by the diene substituents on the π-bound ligand. The observed regioisomers correspond to the product of the most stabilized intermediate pathway, rather than the product of minimum rearrangement. The reactions have been shown to proceed under kinetic control.