Unusual CC Bond Migration in 3-Ylidene-2,5-piperazinediones

Abstract

Treatment of 3‐alkylidene or 3‐benzylidene‐2,5‐piperazinediones 6 with catalytic amounts of acid gives rise to the formation of isomers 7 by migration of the CC bond into the alkyl substituent at position 6, or results in mixtures of racemic 7 and E isomers 8. The existence of tautomeric equilibria is discussed.

Secondary Metabolites from Penicillium pinophilum SD-272, a Marine Sediment-Derived Fungus

“…In addition to compounds 1 – 4 , six known secondary metabolites including N -methylphenyldehydroalanyl- l -prolin-anhydrid ( 5 ) [18,19], cyclo- trans -4-OH-( d )-Pro-( d )-Phe ( 6 ) [20], cyclo( d )-Pro-( d )-Val ( 7 ) [20], rubralide C ( 8 ) [21], 5′-epialtenuene ( 9 ) [22] and altenuene ( 10 ) [22] (Figure 1), were also isolated, and their structures were elucidated by comparing the NMR data with those of literature reports [18,19,20,21,22]. …”

Synthesis of monoalkylidene diketopiperazines and application to the synthesis of barettin

“…1, eqn (2)) to form the desired mono-alkylidene product 7 . Literature precedent suggested that substituted diketopiperazines related to 6 , substrates derived from both natural 11 and unnatural 12 bis-acetoxy DKP substrates, could undergo aldol condensations; however, the mono-acyl DKP intermediate 6 has several more enolizable protons and effective regioselectivity and reactivity was not apparent from precedent. Although a modest hypothesis, if our synthesis plan could be reduced to practice, we reasoned that it would serve as a direct and general strategy for the synthesis of many mono-alkylidene DKP structures, including derivatives with non-natural amino acid substituents.…”

Domino Reaction Sequence for the Synthesis of [2.2.2]Diazabicycloalkenes and Base-Promoted Cycloreversion to 2-Pyridone Alkaloids

“…Because 2 does not contain the lactim ether function, the requisite isomerization is more challenging as compared to the first-generation chemistry. Precedent for an analogous isomerization of DKP alkylidene substrates resembling 2 is restricted to a proline-derived substrate that can be isomerized only under strongly acidic conditions (refluxing HBr 18 or AcCl 19 ). We hoped to realize this isomerization under milder conditions by generating a transient lactim ether 3 , which we anticipated would enable alkene isomerization to 4 and [4 + 2] cycloaddition.…”