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Synthetic studies toward ecteinascidin 743
Xiaochuan Chen1, Jinchun Chen, Michael De Paolis
1Institut de Chimie des Substances Naturelles, CNRS, 91198 Gif-sur-Yvette Cedex, France.
The Journal of Organic Chemistry
|May 21, 2005
Summary
A novel synthetic route efficiently produced a complex tetracycle featuring a 1,4-bridged 10-membered lactone. Key steps included a Pictet-Spengler reaction and enantioselective alkylation, leading to a pentacyclic compound.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
- Medicinal Chemistry
Background:
- Developing efficient synthetic strategies for complex polycyclic molecules is crucial in drug discovery.
- Tetracyclic and pentacyclic scaffolds are prevalent in numerous biologically active natural products and pharmaceuticals.
- Lactone and isoquinoline moieties are important pharmacophores in medicinal chemistry.
Purpose of the Study:
- To develop an efficient and versatile synthetic methodology for constructing a fully functionalized tetracycle (A-B-C-H) containing a 1,4-bridged 10-membered lactone.
- To explore key chemical transformations, including Pictet-Spengler reactions and enantioselective alkylations, for building complex molecular architectures.
- To synthesize a pentacyclic compound through a domino process involving fragmentation and intramolecular cyclization.
Main Methods:
- Phenolic aldol condensation and Pictet-Spengler reactions were employed for initial fragment construction.
- Enantioselective alkylation of a glycine template using a chiral cinchonidium salt enabled access to enantiomerically pure intermediates.
- A domino cyclization process involving deprotection, fragmentation, and lactone formation was utilized, followed by acid-catalyzed transformation to the final pentacyclic product.
Main Results:
- An efficient synthesis of the tetracycle (A-B-C-H) 7, featuring a 1,4-bridged 10-membered lactone, was achieved.
- Key intermediates, including a protected amino diol, free amine, tetrahydroisoquinoline, amino alcohol, and amino aldehyde, were synthesized in high yields.
- A domino cyclization sequence successfully formed the 1,4-bridged 10-membered lactone, and subsequent acid treatment yielded the target pentacyclic compound 51.
Conclusions:
- The developed synthetic route provides an efficient pathway to complex tetracyclic and pentacyclic compounds.
- The study highlights the utility of Pictet-Spengler reactions and enantioselective alkylations in constructing intricate molecular frameworks.
- The domino cyclization strategy offers a powerful tool for the rapid assembly of polycyclic lactone-containing structures.