Studies Toward The Synthesis Of Crinipellin A

Crinipellins is the first natural product containing a tetraquinane skeleton isolated from Crinipellis stipitaria,many of whose family members have important biological activities.It contains a linear cis,trans,cis triquinane(ABC rings)and an angular triquinane(BCD rings)structure,and 8 to 10 stereogenic centers,three of which are contiguous all-carbon quaternary carbons.This structure is quite complex,and the synthesis is great challenging and has attracted the interest of synthetic organic chemists for a long time.This thesis mainly describes the construction of the core tetracyclic skeleton(A-D)of the crinipellins,and further investigation on the total synthesis of crinipellin A with a model substrate,which is mainly divided into the following three parts:In chapter one,the total synthesis advance of some representative natural products containing polycyclic and all-carbon quaternary centers was summarized.In chapter two,a brief review of our group's research background on the synthesis of quaternary carbon-containing polycyclic natural products using semipinacol rearrangement reaction,and a first introduction of the new Nazarov-like cyclization/dicycloexpansion rearrangement reaction developed by our group were described.In chapter three,the isolation,activity study and synthesis of crinipellins were also introduced in detail.On the basis of its angular tricyclic structural characteristic,a synthesis strategy of the crimipellin A was designed by use of the newly developed Nazarov-like cyclization/dicycloexpansion rearrangement reaction as the key step.Efficient construction of the core tetracyclic skeleton was realized from the model substrate and further effort toward the total synthesis of crinipellin A was also made by the successive functional group transformations.