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A novel method for the solid-phase synthesis of bicyclic guanidines has been described in a recent publication (J.M. Ostresh et al., J. Org. Chem., 63, (1998), 8622-8623). Following the preparation of acylated dipeptides (1) on methylbenzhydrylamine-derivatised polystyrene resin, exhaustive reduction using borane-THF generated triamines that could be cyclised using thiocarbonyldiimidazole. The product bicyclic guanidines (2) could be cleaved from the resin beads by treatment with hydrogen fluoride, although there was evidence that the products could also be cleaved with 100% trifluoroacetic acid. Steric factors had a key effect on the cyclisation step: aminoisobutyric acid in the R1 position led to complete cyclisation, whilst in the R2 position, cyclisation was inhibited.
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The sarcodictyins A (1, R = Me) and B (1, R = Et), originally isolated from a soft coral, are complex natural products with potent antitumour activity through a taxol-like mode of action (tubulin polymerisation and microtubule stabilisation). In a recent paper, a solid-phase synthetic route to the s
Whilst ยต-opioid antagonists have been used for many years in the treatment of drug abuse, ฮบ antagonists might provide a more effective and longer-lasting treatment and novel agents provide an attractive target for drug discovery. The library described in this publication was based on 3,4-dimethyl-4-
Obesity is an increasingly common disease in the western world and incidence has been associated with a range of other diseases including hypertension, atherosclerosis and type II (non-insulin dependent) diabetes. However, little is known about the proteins that mediate gene control of lipid metabol