Structure I is a serotonin antagonist. A methyl group has been introduced into analogue II, resulting in significantly decreased activity. Which of the following statements is the most reasonable explanation for the change in activity observed for structure II? The methyl group interacts with an extra hydrophobic binding region through van der Waals interactions. The methyl group increases the basicity of the ring nitrogen, making it a better hydrogen bond donor. The methyl group prevents the pyridine rings from being coplanar and prevents the molecule adopting the active conformation necessary to bind. The methyl group prevents the pyridine from being a good hydrogen bond acceptor Levadopa (structure below) enters the brain more efficiently than dopamine. Once Levadopa enters the brain, enzymes convert it to dopamine, which is the active compound. Considering this, which of the following statements is false? Dopamine is considered a prodrug of levadopa Levadopa is more polar yet crosses the blood brain barrier more effectively. Levadopa mimics an amino acid and takes advantage of transport proteins in order to cross the blood brain barrier. Drugs can be administered to protect Levadopa from metabolism before it reaches the brain Which of the following does not share an isosteric relation with the rest? CH2OFNH SiH2 Which of the following statements best describes a bio-isostere? A group that can be used in place of another group whilst retaining the important biological activity of the drug. A group having the same size as another group A group having the same valency as another group A group that is chemically similar Which of the following strategies would be best to increase the yield of the desired product over the side product in the following reaction? IstartingmaterialIIdesiredproductIIIsideproduct a. Replace propionyl chloride with propionyl anhydride b. Use an excess of compound I in the reaction c. Use an excess of propionyl chloride in the reaction d. Both A and B e. Both A and C