Preparation of spiro[4.4]oxaphospholene and -azaphospholene systems from carbohydrate templates.

Introduction of a spiro-phosphorus cycle in position 3 of monosaccharidic derivatives was studied starting from cyanohydrin or aminonitrile A. A two-step procedure involving (i) phosphonylation and (ii) carbanion-mediated phosphonate intramolecular cyclization (denoted CPIC) was used. The necessity of having an electron-withdrawing group α to the phosphorus atom in order to avoid undesired reactions was demonstrated.