“…[3] As a part of a programme aimed at the design and preparation of polyfunctionalised, chiral building blocks that are useful for the asymmetric synthesis of biologically active nitrogen-containing compounds, we have studied the behaviour of (R)-2-[(S)-1,2-bis(benzyloxy)ethyl]-1-[(S)-1-phenylethyl]-2,3-dihydro-4(1H)-pyridone (1) as a synthetic precursor to obtain chiral 2,3-disubstituted 2,3-dihydro-4(1H)-pyridones in enantiomerically pure form. This synthetic intermediate is easily available on gram scale from inexpensive -mannitol, [4] which comes from renewable sources. The ease with which C-2 and/or C-4 can be functionalised is well illustrated by the expedient asymmetric synthesis of (R)-4-oxopipecolic acid, [5] (2S,4R)-1-(tert-butoxycarbonyl)-N-tert-butyl-4-hydroxypipecolamide, [6] (R)-and (S)-2-substituted 4-alkylidenepiperidines, [7] (2R,4S)-and (2R,4R)-4-phosphonomethylpiperidine-2-carboxylic acids, [8] cis-and trans-1,2,4-trisubstituted piperidines, [9] (R)-quinuclidine-2-carboxylic acid [10] and (2R,4R)-N-(tert-butoxycarbonyl)-4-[2-(methoxycarbonylamino)ethyl]pipecolic acid.…”