Table 1.

Biginelli reactions for the preparation of DHMP acids.^a

Entry	R1	R2	R3	Yield [%]	Product
1	Ph	H	Bn	91	13
2b	Ph	H	H	93	14
3	Ph	CH2CO2H	Et	63	15
4	Ph	CH2CO2H	Bn	78	16
5		H	Et	90	17
6		H	Bn	91	18

^aConditions: 0.10 equiv p-TSA, 110 °C 8–48 h in DMSO. ^bObtained via hydrogenolytic deprotection of product 13 (entry 1). Conditions: H₂ (balloon), 10 wt % Pd/C, acetic acid/ethanol (1:3), 50 °C, 15 h.