Ultrasonic-Assisted Synthesis of Two t-Butoxycarbonylamino Cephalosporin Intermediates on SiO₂

Table 1

Comparison of three methods for the synthesis of Boc-ACLE.

Number	Catalyst	Reaction time	Solvent	Yield%
1	NSA	12 h	CH2Cl2	51 [4]
2	TEBA	10 h	Dioxane/H2O	80 [5]
3	Catalyst-free	8 h	THF	15 [6]

The HPLC assay indicated the yield was 15% according to the reported methods.