Practical methodology for the bis-O-methylation of (3S)-isopropyl-pipe
razine-2,5-dione 4 on a 45 g scale to generate Schollkopf's bis-lactim
ether chiral auxiliary 3S)-3,6-dihydro-2,5-dimethoxy-3-isopropyl-pyra
zine 1 has been developed. Monomethylated intermediates 5 and 6 are re
ported for the first time. The gelling effects of 4 in a range of comm
on solvents are also described. (C) 1998 Elsevier Science Ltd. kll rig
hts reserved.