Fraser-Reid B, Chen X T, Haag D, Henry K J, McPhail A T
Natural Products and Glycotechnology Research Institute, Inc., Durham, North Carolina.
Chirality. 2000 Jun;12(5-6):488-95. doi: 10.1002/(SICI)1520-636X(2000)12:5/6<488::AID-CHIR34>3.0.CO;2-W.
L-Rhamnal is readily converted into an allyl 2, 3-unsaturated-C-glycopyranoside. The (S) configuration of the alphaL-anomer defines the stereochemical outcome of the future IMDA reaction, leading to the absolute stereochemistry for the trans-decalin moiety in naturally occurring terpenoids. Selective cleavage of the terminal double bond of the allyl group provides an aldehydo function which serves for an aldol/Claisen addition with ethyl sorbate. Of the four possible diastereomers, one is obtained in pure form and processed to give the IMDA precursor. Cyclocondensation is achieved by heating in xylene to give a tricyclic trans-decalin whose structure is established by NMR and X-ray analysis.
鼠李醛很容易转化为烯丙基2,3-不饱和-C-吡喃糖苷。α-L-异头物的(S)构型决定了未来IMDA反应的立体化学结果，从而确定了天然萜类化合物中反式十氢萘部分的绝对立体化学。烯丙基末端双键的选择性裂解提供了一个醛基官能团，该官能团用于与山梨酸乙酯进行羟醛/克莱森加成反应。在四种可能的非对映异构体中，以纯形式得到一种，并将其加工得到IMDA前体。通过在二甲苯中加热实现环缩合反应，得到一个三环反式十氢萘，其结构通过核磁共振和X射线分析确定。
