Functionalized Phosphazenes Containing a Ketone Group

A similar approach has been reported for the total synthesis of the marine cyanobacte-rial apratoxin A (111). Apratoxin A, isolated from Lyngbya spp. cyanobacteria, is representative of a growing class of marine cyanobacterial cyclodepsipeptides wherein discrete polypeptide and polyketide domains are merged by ester and amide or amide-derived linkages. For the preparation of apratoxin A, the reaction of the azide 109 with 

The formation of a tetrahydropyridine ring by means of the Staudinger reaction of azido-ketones and phosphines followed by intramolecular Aza-Witig reaction was appUed 

An optically active piperidine ring has been constructed by an intramolecular aza-Wittig reaction allowing a concise enantiospecific synthesis of nuphar piperidine alkaloids, among them (-)-anhydronupharamine (118), which has a sesquiterpenoid structure 

Nigrifactine (114a) (25%) Polonicumtoxin A (114b) (83%) Polonicumtoxin B (114c) (79%) Polonicumtoxin C (114d) (78%) 

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