76582-59-7Relevant academic research and scientific papers
A well-defined monomeric aluminum complex as an efficient and general catalyst in the Meerwein-Ponndorf-Verley reduction
McNerney, Brian,Whittlesey, Bruce,Cordes, David B.,Krempner, Clemens
supporting information, p. 14959 - 14964 (2015/01/08)
The metal-catalyzed Meerwein-Ponndorf-Verley (MPV) reduction allows for the mild and sustainable reduction of aldehydes and ketones but has not found widespread application in organic synthesis due to the high catalyst loading often required to obtain satisfactory yields of the reduced product. We report here on the synthesis and structure of a sterically extremely overloaded siloxide-supported aluminum isopropoxide capable of catalytically reducing a wide range of aldehydes and ketones (52 examples) in excellent yields under mild conditions and with low catalyst loadings. The unseen activity of the developed catalyst system in MPV reductions is due to its unique monomeric nature and the neutral donor isopropanol weakly coordinating to the aluminum center. The present work implies that monomeric aluminum alkoxide catalysts may be attractive alternatives to transition-metalbased systems for the selective reduction of aldehydes and ketones to primary and secondary alcohols.
Sterol C24-methyltransferase: Physio- and stereo-chemical features of the sterol C3 group required for catalytic competence
Howard, Alicia L.,Liu, Jialin,Elmegeed, Gamal A.,Collins, Emily K.,Ganatra, Kalgi S.,Nwogwugwu, Chizaram A.,Nes, W. David
body text, p. 43 - 50 (2012/08/07)
Sterol C24-methyltransferases (24-SMTs) catalyze the electrophilic alkylation of Δ24-sterols to a variety of sterol side chain constructions, and the C3- moiety is the primary determinant for substrate binding by these enzymes. To determine what specific structural features of the C3-polar group ensure sterol catalysis, a series of structurally related C3-analogs of lanosterol that differed in stereochemistry, bulk and electronic properties were examined against the fungal 24-SMT from Paracoccidioides brasiliensis (Pb) which recognize lanosterol as the natural substrate. Analysis of the magnitude of sterol C24-methylation activity (based on the kinetic constants of Vmax/Km and product distributions determined by GC-MS) resulting from changes at the C3-position in which the 3β-OH was replaced by 3α-OH, 3β-acetyl, 3-oxo, 3-OMe, 3β-F, 3β-NH2 (protonated species) or 3H group revealed that lanosterol and five substrate analogs were catalyzed and yielded identical side chain products whereas neither the 3H- or 3α-OH lanosterol derivatives were productively bound. Taken together, our results demonstrate a chemical complementarity involving hydrogen bonding formation of specific active site contacts to the nucleophilic C3-group of sterol is required for proper orientation of the substrate C-methyl intermediate in the activated complex.
PROCESS FOR THE PREPARATION OF LANOSTA-8-ENE COMPOU
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Page/Page column 4-5, (2010/04/03)
The present invention concerns a process for the preparation of lanosta-8-ene compounds having lanosta-8-ene-7-one or lanosta-8-ene-7-ol compounds as starting material.
Une voie d'acces a la trimethyl-4,4,7a tetrahydro-3aα,4,7,7aα (3H)-benzofurannone-2 a partir des alcoxy-5 trimethyl-4,4,7a hexahydro-3aα,4,5,6,7,7aα (3H)-benzofurannones-2
Rouessac, Annick,Rouessac, Francis,Zamarlik, Henri
, p. 199 - 203 (2007/10/02)
The 5-hydroxy 4,4,7a-trimethyl 3aα, 4,5,6,7,7aα-hexahydro (3H)-benzofuran-2-ones are obtained by cleavage of the corresponding methyl or ethyl ethers with iodotrimethylsilane.The two hydroxylactones 5 and 6 are transformed into sulfonic esters as a step towards the dehydrated lactone 7, without squeletal rearrangement.Solvolysis of the tosylate and the mesylate of 5, a cis-fused ring lactone, proceeds by completely different ways under analogous experimental procedures.Results are explained and compared to the solvolysis of some triterpenes.Experimental procedures for ether cleavage are discussed and the intermediates or by-products of these reactions are identified.
