The highly diastereoselective alkylation of 6-methylperihydropyrimidin-4-ones 1 and 2 has been reported. The corresponding lithium enolates have been alkylated under a variety of conditions with good trans selectivity and all the reaction products have been easily separated and characterised.
The synthesis of 6-methyl perihydropyrimidin-4-ones (1'S,6R)-3a and (1'S,6S)-3b is reported starting from rac-3-aminobutanoic acid. The aldol condensation of various metal enolates of 3a and 3b with benzaldehyde and acetaldehyde is reported. All reactions afford complete facial diastereoselectivity and good simple diastereoselectivity, depending on the nature of the enolate and of the aldehyde. The reaction yields are generally good and the aldols have been characterized by means of H-1 NMR spectroscopy and NOEDIFF experiments.
Formation of Aziridine-2-amides through 5-Halo-6-methylperhydropyrimidin-4-ones. A Route to Enantiopure <scp>l</scp>- and <scp>d</scp>-Threonine and <i>allo</i>-Threonine