116802-24-5Relevant academic research and scientific papers
Synthesis of a new (1R)-(-)-myrtenal-derived dioxadithiadodecacycle and its use as an efficient chiral auxiliary
Vargas-Diaz, M. Elena,Joseph-Nathan, Pedro,Tamariz, Joaquin,Zepeda, L. Gerardo
, p. 13 - 16 (2007/10/03)
(Chemical Equation Presented) The new macrocycle 9 (>70% yield from hydroxythiol 10) was treated with several nucleophilic reagents (RMgX, RLi, and LiAlH4) affording carbinols 12a-j (80-96% yield, >99:1 dr). Oxidative hydrolysis of 12a,c,e, followed by LiAlH4 reduction of the resulting mixture, gave 16a,c,e in >95% ee,16c being a key precursor for the preparation of fungicide 17. The absolute configuration of 9 and 12j (Nu = H) was established by single-crystal X-ray diffraction analyses and chemical correlation.
Catalytic asymmetric rearrangement of α,α-disubstituted α-siloxy aldehydes to optically active acyloins using axially chiral organoaluminum Lewis acids
Ooi, Takashi,Ohmatsu, Kohsuke,Maruoka, Keiji
, p. 2410 - 2411 (2007/10/03)
A catalytic asymmetric rearrangement of α,α-dialkyl-α-siloxy aldehydes has been developed based on the design of a stereochemically defined, axially chiral organoaluminum Lewis acid 3. For instance, treatment of (S,S)-4 (1.1 equiv) with Me3Al in toluene at room temperature for 30 min generated (S,S)-3 (5 mol %), and subsequent reaction with α-siloxy aldehyde 1a (R = CH2Ph) at -20 °C for 12 h resulted in the smooth rearrangement to afford the corresponding α-siloxy ketone 2a (R = CH2Ph) in 96% isolated yield with 87% ee (S). The scope of this unprecedented stereoselective rearrangement has been investigated with representative substrates, in which impressive kinetic resolution of racemic, α,α-disubstituted α-siloxy aldehydes has also been achieved. These results clearly demonstrate the utility of the present approach for the catalytic enantioselective synthesis of various acyloins and tertiary α-hydroxy aldehydes not readily accessible by the previously known asymmetric methodologies. Copyright
Diastereoselective addition of grignard reagents to chiral α-ketoimides derived from Oppolzer's sultam
Raszplewicz,Sikorska,Kiegiel,Balakier,Jurczak
, p. 1901 - 1907 (2007/10/03)
Additions of various Grignard reagents to N-pyruvoyl- (3) and N-phenylglyoxyloyl-(2R)-bornane-10,2-sultam (4) under thermal and Lewis-acid catalytic conditions are studied. High diastereoselectivity was observed in these reactions, and in the case of vinylmagnesium bromide additions to α-ketoimide 4 a change of direction of asymmetric induction was found.
Lipase AKG mediated resolutions of α,α-disubstituted 1,2-diols in organic solvents; remarkably high regio- and enantio-selectivity
Hof, Robert P.,Kellogg, Richard M.
, p. 2051 - 2060 (2007/10/03)
Diols 1, which contain adjacent tertiary and primary hydroxy groups, can be selectively mono-acylated at the primary hydroxy group by many lipases in organic solvents. Since the reaction does not take place at the chiral tertiary centre itself, observed enantioselectivities are usually low. Only the combination of one lipase, lipase AKG (Amano, Pseudomonas sp.), with selected substrates gives high enantioselectivities (E 20 to > 200). Also, the solvent and acyl donor employed influences the outcome. On the basis of the results of lipase AKG towards substrates 1 an active site model for this specific lipase has been developed, which can account for the results obtained. Full experimental details on the synthesis of diols 1 and enzymatic preparation of acetates 2 are given. Also, the absolute stereochemistry of the enzymatically prepared diols 1 has been established by independent synthesis from (R)-mandelic acid.
Process for the preparation of optically active 2-hydroxyethyl-azole derivatives
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, (2008/06/13)
A process for the preparation of an optically active 2-hydroxyethyl-azole derivative of the formula STR1 in which X represents a nitrogen atom or a CH group, comprising (a) in a first stage, reacting an optically active diol of the formula STR2 with a tos
