Mitsunobu procedure ring closure

The Mitsunobu procedure has found considerable application, so it has been used for diolide formation in pyrenophorin (equation 138) °° and colletodioF° syntheses. Yamaguchi s method is much infe-rior. As expected, the ring closure in equation (138) proceeds with inversion of configuration. In a... 

A more recent report discussed the traceless solid-phase preparation of phthali-mides by cyclative cleavage from conventional Wang resin [63]. To find the optimum conditions for the cyclative cleavage step, ortho-phthalic acid was chosen as the model compound and was attached to the polystyrene resin via a Mitsunobu procedure. Use of N,N-dimethylformamide as a solvent for the cyclative cleavage furnished the desired compounds in high yield and excellent purity (Scheme 16.42). The type of amine had an effect on the outcome of the reaction, however. Aromatic amines could not be included in the study because auto-induced ring-closure occurred during conversion of the polymer-bound phthalic acid. 

The aziridine-ring closure based on the Mitsunobu reaction, the Staudinger reaction, and isomerization of aminooxiranes also involves nucleophilic displacement as the key step of the reaction mechanism. Other reactions rarely reported in the synthesis of carbohydrate aziridines involve nonstandard, " even unusual procedures lacking a general application. 

Unfortunately, an identical approach failed for the synthesis of (-l-)-australine (96) since a Mitsunobu ring closure of the second ring did not take place. A few years later, however, Trost and coworkers pubhshed a different route that made an RCM-mediated synthesis of (-t-)-austrahne (96) possible. In a similar procedure as... 

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