Question

4. (16 pts) The drug Buspirone, marketed as Buspar Tabs "M, is an anxiolytic agent and a serotonin receptor agonist belonging to the azaspirodecanedione class of compounds. Its structure is unrelated to those of the benzodiazepine anti-anxiety agents, but it has an efficacy comparable to diazepam (Valium TM). It is used for the management of GAD, generalized anxiety disorders. [Ref: PubChem/DrugBank 13 15 12 11 16 N 18 10 28 24 20 27 21 Buspirone, Buspar Tabs 26 a. (2 pts) How many chiral stereocenters are present in this structure? b. (2 pts) Where would the C-O groups absorb in the IR? (Hint: the imide ring is a twist chair -how can this influence the structure and the frequencies?) 1740cm 1650 cm 1685 cm 1715 cm c. (2 pts) In the 'H-NMR spectrum, the range of the aromatic hydrogens is probably? d. (2 pts) In the 'H-NMR spectrum, where would you expect to find the hydrogens connected to C-10 and C-18? Use a range of 0.5 8 units. e. (3 pts) In the c-NMR spectrum, identify by number, which carbons will have absorbances at: 161 ppm 116ppmX 157ppm_ If more than one carbon will occur at the given frequency, please note this 172ppm f. (2 pts) How many unique "C signals will be seen in the spectrum? g (3 pts) The Mass spectrum of this compound will: Have an ever or odd parent ion mass? Would you expect a significant value for the M to M+2 ratio? -Show an M+ 1 intensity of approximately 20-25%, 25-30%, 30-35%?

Answer 1

Part a. No. of chiral stereocenters = 0

Part b. 1685 cm^-1

Part c. 6.5 - 8.0 ppm

Part d. 3.15 ppm

Part e. 116 ppm = C-15; 157 ppm = C-14, C-16; 161 ppm = C-12; C-2. C-20

Part f. 10