ABSTRACT
A short formal synthesis of ent-Cephalotaxine is achieved. The approach features a new Lewis acid-mediated [2,3]-Stevens rearrangement of N-allylated prolineamide to generate a key quaternary stereogenic center. Additionally, a one-pot Parham-aldol sequence was developed to rapidly assemble two of the four rings in the cephalotaxine core.
Subject(s)
Homoharringtonine/chemistry , Homoharringtonine/chemical synthesis , Amides/chemistry , Chemistry Techniques, Synthetic , Cyclization , Lewis Acids/chemistry , StereoisomerismABSTRACT
A robust and scalable route to the taccalonolide skeleton starting from trans-androsterone is presented. The synthesis features a cyclic hydroboration carbonylation reaction, which effectively establishes the trans-hydrindane DE ring junction in a remarkable annulation reaction, as well as a Claisen rearrangement and a catalytic Ullmann-type cyclization. This work is part of a larger effort to uncover new clinical candidates from the taccalonolide class of anticancer agents through advances in chemical synthesis.
Subject(s)
Lactones/chemistry , Androsterone , Cyclization , Molecular Structure , StereoisomerismABSTRACT
A Diels-Alder reaction is used as a key step in a synthetic study toward communesin F, in order to simultaneously introduce both of the all-carbon quaternary stereocenters with complete control of relative stereochemistry. Further manipulations of the cycloadduct, toward the hexacyclic core-structure of communesin F, are also disclosed.
Subject(s)
Cycloaddition Reaction/methods , Heterocyclic Compounds, 4 or More Rings/chemistry , Heterocyclic Compounds, 4 or More Rings/chemical synthesis , Polycyclic Compounds/chemistry , Molecular Structure , StereoisomerismABSTRACT
The addition of sterically demanding enolsilanes to alpha-chloro aldehydes results unexpectedly in preferential formation of the anti-PFA product (1,2-syn), while the addition of the corresponding boron enolate furnishes the expected polar Felkin-Anh product (1,2-anti). A stereoinduction model explaining these observations is proposed.