Isothiazoles as auxiliaries and reagents in organic syntheses

Oppolzer s camphor sultam, a well known chiral auxiliary, has been applied to the asymmetric synthesis of chial fluorine-containing amino acids 07OL2513 . Photoinduced addition of perfluoroalkyl iodides 189 to /V-acyloylcamphorsultam 188 in the presence of an aqueous solution of sodium sulfite provides alkyl iodides 190 with moderate to good stereoselectivities. Azide displacement with the major diastereomer of 190 proceeds with inversion of configuration. Subsequent removal of the sultam auxiliary and hydrogenation of the azide afford the chiral fluorine-containing amino acid 192. 

CC 2Me preferably coordinates to the silver metal. Oppolzer s readily removable camphor sultam not only enforces absolute stereocontrol but also enables the underlying reaction cascade (presumably by lowering the pKa of the glycyl a-proton). Pyrrolidine 199 is converted to diol 200 by a 12-step reaction sequence. Since compound 200 corresponds to an advanced intermediate that has been converted to cyanocyline A 87JA1587 , attainment of 200 constitutes an efficient formal synthesis of this natural product. 

The asymmetric [C+NC+CC] coupling reaction can be catalyzed by copper(I) iodide in an exo-selective fashion to provide a diverse array of 4,5-trans substituted pyrrolidines 205 07TL3867 . This reaction complements and extends the Ag(I)-catalyzed ew/o-sclective asymmetric [C+NC+CC] coupling reaction described above. The general procedure involves 

Cu(MeCN)4PF6 or CuOAc dppb or dppf DMSO, rt 

EWG = COzMe, SOzPh, COz-f-Bu R = alkyl, BnOCH2, Ph, PhCH=CH, (S)-CH(CH2Ph)NHBoc 

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