SYNTHESIS OF A HIGHLY FUNCTIONALIZED CARBON RING SKELETON FOR THE TRICHOTHECENE ANGUIDINE

A strategy directed toward the synthesis of the highly functionalized trichothecene anguidine (1) is detailed. The route entails several challenges. The first of these is the synthesis of the congested, achiral cyclopentadienyl malondialdehyde 8, which is induced to undergo a highly diastereoselective, but modestly enantioselective, carbonyl ene reaction to give hydroxy aldehyde 7 under the influence of europium catalysts. The cyclopentadiene ring of 22d is transformed into the bis(allyloxy) epoxide functionality of 33c, which cyclizes regioselectively with ZnBr2 to the tetracycle 35. A new method using (Ph3P)4RhH for the deprotection of the allyl ethers is described. Selective functionalization of the C3, C4, and C12 hydroxyl groups of triol 40a can be accomplished, but isomerization of the exocyclic olefin of tetraacetate 48b gives the Δ8,9 olefin 49 and not the desired Δ9,10 olefin 50. © 1993, IEEE. All rights reserved. © 1990, American Chemical Society. All rights reserved.