Marc A. Grundl

Photochemical Synthesis of Prochiral Dialkyl 3,3-Dialkylcyclopropene-1,2-dicarboxylates with Facial Shielding Substituents and Related Substrates

Different types of cyclopropene-1,2-dicarboxylates 1 have been obtained by photochemical methods from the corresponding pyrazoles 11, 12, or 13. These pyrazoles were synthesized by 1,3-dipolar cycloadditions of alkynes 8 or 9 with either preformed diazoalkanes or diazoalkanes generated photochemically in situ, by use of oxadiazolines as diazoalkane precursors. The numerous substrates have clearly established the scope and limitations of the syntheses of the precursors and the cyclopropenes by the different routes; even prochiral and enantiomerically pure chiral derivatives could be synthesized. Numerous precursors and cyclopropenes could be characterized by X-ray crystal structure analyses, which revealed interesting structural features and allowed unequivocal assignment of different diastereomers or constitutional isomers. Some of the photochemical reactions produced unique side-products; the crystal structure analyses were absolutely crucial for unambiguous structural assignment here.

Bioconjugates of Enantiomerically Pure Organopalladium Compounds by Metal‐Assisted Positional Selective Transesterifications at Palladium Enolates

The synthesis of enantiomerically pure palladatricyclo[4.1.0.0(2,4)]heptanes and their modification by an unprecedented and very efficient positional selective transesterification is described. The mild reaction conditions are most probably based on an acceleration of the transesterification due to assistance by the metal. This novel approach allows straightforward access to a large number of structurally diverse organometallic complexes. The functional groups on the newly installed ester moieties were modified by using standard peptide synthesis protocols, Sonogashira reactions, and nucleophilic substitution reactions. The cellular uptake of these organometallic species was traced by confocal microscopy and their biological activity was evaluated by using different cell lines. Inhibition of cell growth and induction of apoptotic cell death by these novel palladium heterocycles are equivalent to Cisplatin.

Pseudosymmetry and phase transition in dimethyl 2,3-bis(tricyclo[3.3.1.13,7]dec-2-ylidene)butanedioate

The crystal structure of the title compound, C(26)H(34)O(4), shows a reversible phase transition at about 178 K. The structure of the high-temperature phase contains two independent molecules related by pseudosymmetry elements. Cooling through the phase-transition temperature results in a doubling of the c axis. The low-temperature structure contains four independent molecules related by pseudosymmetry elements. The phase transition results in a rearrangement of some weak intermolecular C-H.O interactions. The number of very weak C-H.O interactions, with H.O distances between 2.8 and 2.9 A, is increased in the low-temperature structure.

Di­methyl di­spiro­[tri­cyclo­[3.3.1.13,7]­decane-1,2′-bi­cyclo­[1.1.0]­butane-4′,1′′-tri­cyclo­[3.3.1.13,7]­decane]-1′,3′-di­carboxyl­ate, a strain-enhanced bicyclo[1.1.0]­butane with a very short intramolecular C—H⋯H—C contact

The title molecule, C(26)H(34)O(4), shows a very short repulsive intramolecular C-H.H-C contact, with an H.H distance of only 1.71 A. The flap angle varphi of the bicyclo[1.1.0]butane group is widened to 131.23 (8) degrees. Both methylene C atoms show tilt angles of 6.1 degrees. Bond lengths in the fused cyclopropane rings range from 1.501 (1) to 1.542 (1) A and are influenced by pi interactions with the carboxylate substituents.