Synthetic approaches to quasimarin

Quasimarin, along with the closely related compound bruceantin, has exhibited potent antineoplastic activity. As a result of this activity, both compounds have become the object of considerable synthetic interest. Their complex pentacyclic structures and high degree of oxygenation makes them a formidable synthetic challenge;A program was undertaken to develop a route to the ring system of quasimarin. An aromatic pentacyclic system was successfully produced in ten steps which includes functionality appropriate for further elaboration to quasimarin;An improved route to the carbocyclic system of quasimarin was developed based on the Diels-Alder cyclization of substituted benzylidine and alkylidine isopropylidine malonates. The scope of this cyclization was shown, and an intermediate was made that should prove useful for the total synthesis of quasimarin

Synthetic approaches to quasimarin

Quasimarin, along with the closely related compound bruceantin, has exhibited potent antineoplastic activity. As a result of this activity, both compounds have become the object of considerable synthetic interest. Their complex pentacyclic structures and high degree of oxygenation makes them a formidable synthetic challenge;A program was undertaken to develop a route to the ring system of quasimarin. An aromatic pentacyclic system was successfully produced in ten steps which includes functionality appropriate for further elaboration to quasimarin;An improved route to the carbocyclic system of quasimarin was developed based on the Diels-Alder cyclization of substituted benzylidine and alkylidine isopropylidine malonates. The scope of this cyclization was shown, and an intermediate was made that should prove useful for the total synthesis of quasimarin.</p

Synthesis of a precursor to quassimarin

An intermediate containing the ACE ring system of quassimarin was prepared. The isopropylidene malonate 8 reacted with diene 2 to afford two Diels-Alder adducts. The major adduct was converted into lactone 11 by a sequence involving epoxidation followed by acid-mediated epoxide opening and lactonization.Reprinted (adapted) with permission from The Journal of Organic Chemistry, 51(17); 3347-3350. Doi: 10.1021/jo00367a017. Copyright 1986 American Chemical Society.</p