Surface-Confined Macrocyclization via Dynamic Covalent Chemistry

Surface-confined synthesis is a promising approach to build complex molecular nanostructures including macrocycles. However, despite the recent advances in on-surface macrocyclization under ultrahigh vacuum, selective synthesis of monodisperse and multicomponent macrocycles remains a challenge. Here, we report on an on-surface formation of [6 + 6] Schiff-base macrocycles via dynamic covalent chemistry. The macrocycles form two-dimensional crystalline domains on the micrometer scale, enabled by dynamic conversion of open-chain oligomers into well-defined ∼3.0 nm hexagonal macrocycles. We further show that by tailoring the length of the alkyl substituents, it is possible to control which of three possible products - oligomers, macrocycles, or polymers - will form at the surface. In situ scanning tunneling microscopy imaging combined with density functional theory calculations and molecular dynamics simulations unravel the synergistic effect of surface confinement and solvent in leading to preferential on-surface macrocyclization

Addition of clopidogrel to aspirin and fibrinolytic therapy for myocardial infarction with ST-segment elevation

BACKGROUND: A substantial proportion of patients receiving fibrinolytic therapy for myocardial infarction with ST-segment elevation have inadequate reperfusion or reocclusion of the infarct-related artery, leading to an increased risk of complications and death. METHODS: We enrolled 3491 patients, 18 to 75 years of age, who presented within 12 hours after the onset of an ST-elevation myocardial infarction and randomly assigned them to receive clopidogrel (300-mg loading dose, followed by 75 mg once daily) or placebo. Patients received a fibrinolytic agent, aspirin, and when appropriate, heparin (dispensed according to body weight) and were scheduled to undergo angiography 48 to 192 hours after the start of study medication. The primary efficacy end point was a composite of an occluded infarct-related artery (defined by a Thrombolysis in Myocardial Infarction flow grade of 0 or 1) on angiography or death or recurrent myocardial infarction before angiography. RESULTS: The rates of the primary efficacy end point were 21.7 percent in the placebo group and 15.0 percent in the clopidogrel group, representing an absolute reduction of 6.7 percentage points in the rate and a 36 percent reduction in the odds of the end point with clopidogrel therapy (95 percent confidence interval, 24 to 47 percent; P<0.001). By 30 days, clopidogrel therapy reduced the odds of the composite end point of death from cardiovascular causes, recurrent myocardial infarction, or recurrent ischemia leading to the need for urgent revascularization by 20 percent (from 14.1 to 11.6 percent, P=0.03). The rates of major bleeding and intracranial hemorrhage were similar in the two groups. CONCLUSIONS: In patients 75 years of age or younger who have myocardial infarction with ST-segment elevation and who receive aspirin and a standard fibrinolytic regimen, the addition of clopidogrel improves the patency rate of the infarct-related artery and reduces ischemic complications