Ring contraction of methyl 2,3-anhydro-6-deoxy-6-(furfurylthio)-alpha-D-allopyranoside with LiBr/TMU in boiling toluene gave the corresponding alpha,beta-unsaturated furanosidic aldehyde 1 together with a small amount of the corresponding oxanorbornene Diels-Alder adduct 2. Pumping a mixture of heptane and Et(3)N slowly through a SiO(2) column containing 1 and 2 shifted the ratio strongly toward 2
                                    在沸腾的
甲苯中,用LiBr / TMU对2,3,3-脱
水-6-脱氧-6-(糠
硫基)-α-D-
吡喃
果糖苷进行环收缩,可得到相应的α,β-不饱和
呋喃硅醛1和少量的相应的氧杂
降冰片烯Diels-Alder加合物2。缓慢将
庚烷和Et(3)N的混合物泵送通过包含1和2的SiO(2)色谱柱,使比率强烈地移向2。产物用EtOAc / EtOH和EtOH洗脱。色谱分离得到纯2和1,产率分别为79%和15%。使化合物2进行多种氧化和还原,从而得到氧杂
硼烷烷4-15。结构是通过2D(1)H和(13)C NMR技术以及化合物5的单晶X射线研究确定的。