An efficient chiral phosphoric acid catalyzed Biginelli reaction for the synthesis
of optically pure 4-alkyl-3,4-dihydropyrimidin-2-(1H)-ones has been developed, with a wide range of the desired products being obtained
in moderate to high yields with good to excellent enantioselectivities (up to >99%
ee after one recrystallization). The synthetic utility of this reaction is illustrated
in various aliphatic bicyclic guanidine compounds, which is applied in the formal
synthesis of the bicyclic guanidine core of crambescin A and batzelladine A.
Key words
Biginelli reaction - dihydropyrimidinone - aliphatic aldehydes - crambescin - batzelladine
