Spiro[indolizidine-1,3′-oxindole] compounds have been synthesized in enantiomerically pure form from l-glutamic acid. The key oxidative ring contraction of chiral indolo[2,3-a]quinolizidinone was achieved by treatment with N-bromosuccinimide in tetrahydrofuran/water in the presence of catalytic trifluoroacetic acid. The stereochemistry of the reaction was controlled by the dibenzylamino group which could be subsequently removed using Cope elimination.

中文翻译：

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由L-谷氨酸合成螺[吲哚并咪唑-1,3'-羟吲哚]

螺[吲哚并咪唑-1，3′-羟吲哚]化合物是由1-谷氨酸以对映体纯形式合成的。在催化三氟乙酸存在下，在四氢呋喃/水中用N-溴代琥珀酰亚胺处理手性吲哚并[2,3-a]喹喔啉酮的关键氧化环收缩作用。反应的立体化学由二苄基氨基控制，随后可以使用Cope消除法将其除去。