Eguchi protocol

Grieder and Thomas prepared a diverse library of natural product-like benzodiazepine-quinazolinone alkaloids similar to the family of circumdatins (Figure 11.72). Starting from benzodiazepinedione derivatives, the synthesis relied on a modified Eguchi protocol using a polymer-supported phosphine-mediated intramolecular aza-Wittig reaction in a key step of the reaction sequence. Following this route two sublibraries of tricyclic derivatives similar to the circumdatins D and E were prepared. 

Quinazoline alkaloids containing the indole skeleton such as tryptanthrin (156) have been constructed via intramolecular aza-Wittig reaction of amide derivatives (Scheme 15.35). The fused quinazoline ring in tryptanthrin (156) could be synthesized efficiently in a one-pot procedure via the consecutive Staudinger/intramolecular aza-Wittig reaction of the corresponding azide 154 with tributylphosphine (Eguchi protocol). 

Utilizing the Eguchi aza-Wittig protocol Snider et al. achieved the total synthesis of the more complex antibiotic (-)-asperUcin 20, known also for its potent cholecystokinin antagonist activity [76-79] (Scheme 21) [242]. L-Tryptophan-derived benzodiazepinedione 94 is converted into the fused quinazolinone 95. 

The intramolecular version of the tandem Staudinger/aza-Wittig reaction is often referred to as Eguchi aza-Wittig protocol (cf. references 14f, 60, 119-120, etc.)... 

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