作者:Kai Meilert、George R. Pettit、Pierre Vogel
DOI:10.1002/hlca.200490136
日期:2004.6
this being due to the tricyclic nature of (−)-20 (methyl pyranoside formation). Compound (−)-19 was converted similarly into the (4′S)-epimeric tricyclic spiroketal (−)-21 that also adopts a similar (3S)-configuration and conformation. Spiroketals (−)-20, (−)-21 and analog (−)-23, i.e., (1R,3S,4′R,5R,6′R)-3′,4′,5′,6′-tetrahydro-6′-[(2S)-2-hydroxybut-3-enyl]-7-methoxyspiro[2,6-dioxabicyclo[3.3.1]nonane-3
将2,2'-亚甲基双[呋喃](1)转化为1-(4 R,6 S))-6-[(2 R)-2,4-二羟基丁基] -2,2-二甲基-1 ,3-二恶烷-4-基} -3-[(2 R,4 R)-四氢-4,6-二羟基-2 H-吡喃-2-基)丙-2-酮((+)- 18)和它的(4小号)差向异构体( - ) - 19用高立体选择性和对映选择性(方案1 - 3)。在酸性甲醇分解下,(+)- 18产生单个螺环,(3 R)-4-(1 R,3 S,4'R,5 R,6 'S,7 R)-3',4',5',6'-四氢-4'-羟基-7-甲氧基螺[2,6-二氧杂双环[3.3.1]壬烷-3,2'-[2 H ]吡喃] -6'-基}丁烷-1,3-二醇((-)- 20),其中螺中心的两个O原子都位于赤道位置,这是由于(-)- 20的三环性质(甲基吡喃糖苷的形成)。将化合物(-)- 19类似地转化为(4 'S)-表异构的三环螺酮体(-)-