Synthetic Chemistry of Cyclopropenone Acetals. Penitricin and Buckminsterfullerene.

Abstract

A variety of substituted cyclopropenone acetals have been prepared and studied for the purpose of gaining further insights into their organometallic and thermal chemistry. Acidic hydrolysis of the acetals gave the corresponding cyclopropenones, among these are a naturally occurring cyclopropenone antibiotic, penitricin. A new class of cysteine protease inhibitor can be realized if the penitricin moiety is contrived as a dipeptide-like binding site. Thermolysisbf substituted cyclopropenone acetals generates vinyl carbene species that undergo [1 + 2] and [3 + 2] cycloadditions to electrondeficient olefins. The cyclopropenone acetal also serves as a precursor to a dipolar trimethylenemethane. The vinyl carbene and the trimethylenemethane species undergo cycloaddition to give buckminsterfullerenes, with which the various organic derivatives of fullerenes generated have been shown to exhibit photo-induced cytotoxicity, DNA cutting activity and enzyme inhibition.

Carbometalation of Cyclopropene. Diastereoselective cis-Addition of Zincated Amides, Esters, and Hydrazones

“…1,2 We report in this paper the first information on the stereochemical course of olefin carbometalation with an R-anion of amide, ester, and hydrazone, which is based on our new finding that these anions bearing a zinc(II) countercation (structures unknown and tentatively shown with structures 2 and 3) 3 are reactive enough to add across the double bond of a cyclopropene acetal 1. 4 This novel carbometalation reaction takes place in a cis-manner with a generally high level of 1,2-diastereoselectivity for the newly formed C-C bond (up to 100% ds). In the reaction of an optically active hydrazone, asymmetric induction takes place with a synthetically useful level of selectivity (87-98% ds) to provide a new synthetic entry to optically active carbonyl derivatives.…”

Cyclopropenone AcetalsSynthesis and Reactions

“…The present paper represents the first comprehensive review specifically focusing on the chemistry of CPAs and their analogues (e.g., nitrogen and sulfur analogues of the acetal) and covers all the experimental data reported before May 2002 on the chemistry of these compounds. Although the chemistry of CPA has been partially addressed in various reviews on strained rings, , cycloadditions, − and organometallic chemistry, − we do not intend to avoid any overlaps, so that this work will be the most comprehensive available.…”

Novel Products from Thermolysis of 5,5-Dimethyl-2,2-diphenoxy-Δ3-1,3,4- oxadiazoline in the Presence of DMAD

“…The three products provide indirect evidence for the equilibration of 8 with 9 , neither of which could be observed directly. Equilibration of cyclopropenes with vinylcarbenes has been proposed before, and it is known to be facile for 3,3-dialkoxycyclopropenes. , Compound 2 presumably arises from intramolecular reaction of the ring-opened species, which can be viewed as a hybrid of a dipole and a π-delocalized vinylcarbene ( 9 ) (Scheme ). Moreover, 3 and 4 are likely to be the result of cycloadditions (of 6 and 7 ) to 8 .…”