Download full text in PDF Opens in a new window. Article suggestions will be shown in a dialog on return to ScienceDirect. ... Please enable JavaScript to use all the features on this page. ... A synthesis of an optically active octahydro-2H-pyrido[1,2-a]pyrazine is presented. The key sequence involved the equilibration of an optically active cis-aldehyde to give the thermodynamic trans-aldehyde that was trapped by nitromethane anion. ... The equilibration of an ...