Intramolecular Michael reaction of methyl (R)-6-(tert-butoxycarbonylamino)oxy-4-hydroxy-2-hexenoate, in turn obtained from tert-butyl (R)-3-hydroxy-4-pentenoate, paved the way to the synthesis of both enantiomers of 2-oxa-6-azabicyclo[3.3.0]octan-3-one (the Geissman–Waiss lactone), a precursor for necine bases. Key intermediates in this approach were represented by enantiomeric bicyclic lactones incorporating
                                    (R)-6-(叔-丁氧基羰基
氨基)氧基-
4-羟基-
2-己烯酸甲酯的分子内迈克尔反应,又是从(R)-3-羟基-
4-戊烯酸叔丁酯获得的,合成2-oxa-6-
氮杂双环[3.3.0] octan-3-one(Geissman-Waiss内酯)的两种对映体(
烟碱的前体)。该方法中的关键中间体以并入[1,2]-恶嗪烷核的对映体双环内酯为代表,该化合物已方便地用于通过合成方案来安装目标化合物的
吡咯烷骨架,其特征在于还原了氮-氧键和分子内小号ñ 2反应。