Synthetic scheme of compounds 23, 24, 33, 34, 35, 38.

<p>Reagents and conditions: i) from <b>1</b> for <b>23</b>, from <b>5</b> for <b>24</b>, from <b>32</b> for <b>33</b>: H<sub>2</sub>SO<sub>4</sub>, MeOH, reflux, 1 h; ii) from <b>32</b>: Py · SO<sub>3</sub>, DMF dry, 120°C, 25 min; iii) CH<sub>3</sub>I, anhydrous K<sub>2</sub>CO<sub>3</sub>, dry DMF, reflux, 1.5 h; iv) 1N NaOH, EtOH.</p>