Studies toward the total syntheses of highly potent cytotoxic alkaloids
including the bromopyrrole alkaloids and indole alkaloids were conducted and are
described. Studies carried out in the course of this dissertation consist of five total syntheses of natural products that include bromopyrrole alkaloids nagelamide A, D and agelastatin D as...
PART I. A deuterium exchange analysis of 2,5-dihydroxyacetanilide (5) in the absence and presence of DHAE II was performed to test the nucleophilicity of the substrate in the absence and presence of catalyst. In addition, inhibition studies using 1,4-dihydroxybenzene were performed to determine the role that the N-acetyl side chain...
The 3-substituded indolic enamide moiety has been found in many marine compounds over the past 20 years. These indolic enamides exhibit various biological properties such as cytotoxic, anthelmintic, antimicrobial and HW-inhibitory activities. Among these indolic enamides, some are (E)-enamides, like coscinamide A and coscinamide B, others are (Z)-configuration in their...
The rhenium (V) complex Tp'ReO₂ (Tp' = hydrido-tris-(3,5-
dimethylpyrazolyl)borate), generated in situ from PPh₃ reduction of
Tp'Re0₃, reacts with small ring heterocycles such as epoxides and
episulf ides. The strained trans-cyclooctene ring provides an unusual
thermodynamic bias against direct atom transfer, but trans-cyclooctene
oxide still produces substantial amounts of trans-cyclooctene....
A series of compounds, 7-8 and 20-25, were tested as competitive inhibitors of 2,5-dihydroxyacetanilide epoxidase I (DHAE I) and DHAE II. A Hammett plot was constructed for each enzyme to determine the effect of electron density on inhibition. DHAE I gave a linear, highly correlated plot (r²=0.91) that signifies the...
In situ reduction of hydrido-tris-(3,5-dimethylpyrazolyl)borato(trioxo) rhenium(V) with triphenylphosphine or triethylphosphite leads to a reactive rhenium(V) species that catalytically deoxygenates epoxides at 75-105°C. The reaction is stereospecific, except for trans- and cis-butene oxide which formed minor amounts of the opposite isomer. A variety of different functional groups were tolerated and even...
The epoxide deoxygenation reaction is formally the reverse of theepoxidation reaction. Compared to epoxidation, which has reached its fullmaturity, epoxide deoxygenation has not been as intensively developed.Among the few deoxygenation reagents, a handful are catalytic in a metalcomplex, show high stereospecificity and operate under mild conditions. Acommon feature of all...
The rhenium dithiodiolate, Hydrido-tris-(3 ,5-dimethyl- 1 -pyrazol yl) borato(ethane- 1 ,2-dithiodiolato)(oxo)rheni um(V), and Hydrido-tris-(3 ,5-dimethyl- 1 -pyrazolyl)borato(phenylethanedithiodiolato)(oxo)rhenium(V), were synthesized by reductive cyclocondensation of alkane-1,2-dithiols with Tp'Re0₃ in a one pot fashion. The rhemium monothiodiolate, Hydrido-tris-(3 ,5-dimethyl- 1 -pyrazolyl) borato(ethane- 1 ,2-monothiodiolato)(oxo)rhenium(V), and Hydrido-tris-(3 ,5- dimethyl- 1 -pyrazolyl)borato(propanemonothiodiolato)(oxo)rhenium(V), were also synthesized...
In situ, reduction of Cp*ReO₃ by PPh₃ to form (Cp*ReO)₂(μ-O)₂ allows catalytic deoxygenation of epoxides, however, conproportionation between Reⱽ and Reⱽᴵᴵ species to form clusters of ((Cp*Re)₃(μ-O)₆}²⁺(ReO₄⁻)2 and new compound {(Cp*Re)₃(μ²-O)₃(μ³-O⁾³ReO₃}⁺(ReO₄⁻) leads to removal of rhenium from the catalytic cycle and loss of activity, The epoxide deoxygenation mediated by (Cp*ReO)₂(μ-O)₂...