Oxetanes: Recent Advances in Synthesis, Reactivity, and.
Chapters 4 and 5 describe studies towards the total synthesis of pyxidatol C. Advanced intermediates were prepared including ester XII and lactone XIII containing the requisite gem-dimethyl substituted 7-membered ring, the cyclopropane moiety and the methyl ketone side chain in place.
The cyclic hydroboration of 2,7-dimethyl-2,6-octadiene (6) was studied. It was found that the stereochemical outcome of the reaction was dependent upon the solvent, temperature, time and the nature of the borane reagent. Pure racemic trans-2,5-diisopropylborolane (14) was isolated following selective complexation of the cis-2,5-diisopropylborolane (15) with 1-(2-hydroxyethyl)-pyrrolidine.
Gold-catalyzed glycosylation using S-but-3-ynyl and gem-dimethyl S-but-3-ynyl thioglycoside donors has been investigated for the synthesis of various types of complex oligosaccharides.It was found that 2,2-dimethyl S-but-3-ynyl thioglycoside donors are more reactive than their S-but-3-ynyl thioglycoside counterparts and gave the glycoside products in relatively higher yields.
Chlorins that bear a gem-dimethyl group, which attributes their resistance to oxidation, are of interest for applications in photomedicine. Herein, we present the synthesis and the photophysical.
Zhang Z, Chen Y, Dolphin D. (2012) Diastereoselective generation of triple-stranded helicates induced by gem-dimethyl groups on a linker. Dalton Transactions (Cambridge, England: 2003). 41: 4751-3 Zhang Z, Chen Y, Dolphin D. ( 2012 ) Diastereoselective generation of triple-stranded helicates induced by gem-dimethyl groups on a linker Dalton Transactions. 41: 4751-4753.
When the alkyne is present at C13 (with no neighboring gem-dimethyl group), the RCEDYM reaction leads to 14,15-isotaxanes 16a,b and 18b with the gem-dimethyl group on the A ring. If the alkyne is at the C11 position (and thus flanked by a gem-dimethyl group), RCEDYM reaction only proceeds in the presence of a trisubstituted olefin at C13, which disfavors the competing diene ring-closing.
N,N-Dimethyl-4-aminoazobenzene azoreductase and laurate hydroxylase activities in control hepatocytes retained their response to clofibrate for up to 96 hr, although the response gradually diminished after 24 hr. In all cases, maximal induction of both enzyme activities was observed 72 hr after addition of drug. Phenobarbital and beta-naphthoflavone did not induce N,N-dimethyl-4.