Table 5.

The yields, colours, and ESI-MS data of Cds. 15–18.

	Cd. 15	Cd. 16	Cd. 17	Cd. 18
Yield (%)	84.1	85.7	85.5	87.3
Color	White powder	Yellow needle crystal	White powder	White powder
m.p. (°C)	61–62	285–286	188–189	228–229
ESI-MS (m/z)	306.3 b	300.62 b	334.4 a	326.2 b

^a [M + 1]⁺; ^b [M − 1]⁻.