Formal total synthesis of fostriecin by 1,4-asymmetric induction with an alkyne-cobalt complex.

The synthesis of a protected dephosphofostriecin, and thereby a formal synthesis of fostriecin, has been accomplished. The synthetic challenges were the construction of four stereogenic centers and the conformationally labile cis-cis-trans-triene moiety. Previous total syntheses have employed at least two asymmetric reactions that required the use of an external chiral auxiliary.

Diphenylprolinol silyl ether catalysis in an asymmetric formal carbo [3 + 3] cycloaddition reaction via a domino Michael/Knoevenagel condensation.

Diphenylprolinol silyl ether was found to catalyze the formal carbo [3 + 3] cycloaddition reaction through the domino reaction via the Michael reaction, followed by Knoevenagel condensation of the alpha,beta-unsaturated aldehyde and dimethyl 3-oxopentanedioate, affording substituted cyclohexenone derivatives with excellent enantioselectivity.

Formal total synthesis of fostriecin via 1,4-asymmetric induction using cobalt-alkyne complex.

The synthesis of a protected dephosphofostriecin, and thereby a formal synthesis of fostriecin, has been accomplished. Two of the four chiral centers are controlled by an external chiral auxiliary and the other two are synthesized stereoselectively, one by a novel 1,4-asymmetric induction using cobalt-alkyne complex, and the other by 1,3-asymmetric induction.