Scheme 1.

Synthetic route and chemical structures of compounds 4–6 and 7a–7x. Reagents and conditions: (a) i: benzaldehyde, methanol, r.t.; ii: NaBH₄, r.t., 98%; (b) α-ketoglutaric acid, p-TSA, dry toluene: dioxane = 3:2, DST, reflux, 83%; (c) HCOONH₄, 5% Pd/C, methanol: toluene = 1:1, reflux, 75%; (d) 5% Pd/C, xylene, reflux, 90%; (e) BBr₃, dry DCM, −78 °C to r.t., 63%; (f) acyl chloride, TEA, dry DCM, 0 °C, 48%–86%.

7a: R = C6H5	7g: R = 3′-ClC6H4	7m: R = 4′-FC6H4	7s: R = CH3
7b: R = 2′-pyridyl	7h: R = 4′-ClC6H4	7n: R = 2′-CF3C6H4	7t: R = CH3CH2
7c: R = 2′-CH3C6H4	7i: R = 2′,4′-Cl2C6H3	70: R = 3′-CF3C6H4	7u: R = CH3(CH2)2
7d: R = 3′-CH3C6H4	7j: R = 4′-CH3OC6H4	7p: R = 4′-CF3C6H4	7v: R = CH3(CH2)3
7e: R = 4′-CH3C6H4	7k: R = 2′-FC6H4	7q: R = 1′-naphthyl	7w: R = CH3(CH2)4
7f: R = 2′-ClC6H4	7l: R = 3′-FC6H4	7r: R = 2′-naphthyl	7x: R = CH3(CH2)10