David E. Graves

Studies directed toward the total synthesis of azaspiracid. Construction of the C1–C19 carbon backbone and synthesis of the C10, C13 nonnatural transoidal bisspirocyclic ring system

Abstract The efficient entry to the C 1 –C 19 carbon backbone of azaspiracid is outlined utilizing a key Julia coupling strategy. Spirocyclization of a C 12 sulfone substrate induced formation of the unprecedented, nonnatural transoidal bisspiroketal. Construction of the bisspirocyclic array at C 10 and C 13 , in the absence of the C 12 sulfone, led to formation of the cisoidal orientation of the bisspirocycle, with the nonnatural stereochemistry at C 13 .

CHEMICAL CROSS-LINKING OF ETHIDIUM TO DNA BY GLYOXAL

Ethidium was found to be efficiently cross-linked to DNA by glyoxal. Kinetic studies showed that the rate of the cross-linking reaction is strongly dependent on the glyoxal concentration. Comparative studies using a series of phenanthridines and acridines showed that NH2 groups at both the 2 and 7 positions on the phenanthridine ring are necessary for efficient cross-linking. Studies using synthetic polydeoxynucleotides showed that the 2-amino group of guanine is absolutely required for cross-linking. Fluorescence contact energy transfer and relative viscosity experiments showed that the cross-linked drug remains intercalated into DNA. DNA gel electrophoresis and melting studies demonstrated that cross-linked ethidium does not dissociate the DNA double helix to single strands.

INTRAMOLECULAR FLUORESCENCE QUENCHING IN COVALENT ACRYLAMIDE-INDOLE ADDUCTS

Abstract— Indole derivatives have been prepared which have a covalently linked quencher, acrylamide. One of these adducts, N‐acrylyltryptamine, has a flexible linkage and the other, N‐acrylyl‐1,2,3,4‐tetrahydropyridoindole, has a rigid bridge between indole and the quencher. The intensity decays of these adducts were obtained using multi‐frequency phase and modulation fluorometry. The fluorescence of these adducts appears to be dynamically quenched; dominant lifetimes of 64 ps and 31 ps are found for the flexible and rigid adducts. This indicates that very rapid intramolecular quenching occurs, even when the quencher and fluorophore cannot collide. Quenching in the rigid molecule probably involves electron transfer through two sigma bonds. Anisotropy decay data were also collected and rotational correlation times of 62 ps and 163 ps are reported for the flexibile and rigid adducts, respectively.

Interaction of 7-aminoactinomycin D with single- and double-stranded DNA oligonucleotides

7-Aminoactinomycin D is a potent inhibitor of RNA polymerase and it has been demonstrated to bind to a single stranded DNA. Wadkins and Jovin showed that there is a 20 to 40 fold enhancement in the fluorescence of 7-aminoactinomycin D upon binding to certain single stranded DNA sequences. We report studies of the thermodynamics of the binding of the parent drug, actinomycin D, to single and double stranded DNA. A five-fold range of association constants is found for the different binding sequences that we have investigated. We will correlate these thermodynamic studies with measurements of the fluorescence enhancement, lifetime, and rotational correlation time of the drug bound to the various single and double stranded oligonucleotides.