p. 471 - 473
(1999)(5R,6S)-6-[(R)-1-hydroxyethyl]-3,7-dioxo-1-azabicyclo[3.2.0]heptane-2-carboxylic acid p-nitrobenzyl ester
t-butyldimethylsiyl triflate
(5R,6S)-6-((R)-1-Hydroxy-ethyl)-7-oxo-3-(toluene-4-sulfonyloxy)-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester