Mild, Racemization Free Cleavage of Ketone SAMP-Hydrazones with Oxalic Acid - Recycling of the Chiral Auxiliary
作者:Dieter Enders、Thomas Hundertmark、Ryszard Lazny
DOI:10.1055/s-1998-1765
日期:1998.7
Cleavage of ketone SAMP-hydrazones 1a-f with a saturated aqueous oxalic acid solution gives the corresponding ketones 2a-f in excellent yields and with high enantiomeric purity (ee = 90-99%). The chiral auxiliary SAMP is recovered from the aqueous phase in good yield (85%) and with unchanged enantiomeric purity. This racemisation free cleavage procedure is compatible with functionalities sensitive to oxidative cleavage conditions, such as ozonolysis, or to strong acids.
New Simple Polymeric Supports with Hydrazone Linkers for Solid-Phase Synthesis of Ketones and Primary Amines
作者:Ryszard Lazny、Aneta Nodzewska、Karol Wolosewicz
DOI:10.1055/s-2003-42483
日期:——
The preparation of new solid supports with hydrazine anchoring groups and their application to solid-phase synthesis of ketones and primary amines are described. The supports were used for immobilization of ketones, 4-tert-butylcyclohexanone, pentan-3-one, acetone, N-methylpiperidone, N-benzylpiperidone, and tropinone in the form of their hydrazones. The polymer-supported hydrazones were subjected to deprotonation/alkylation procedure (LDA/RX) once or twice. The resulting alkylated products were cleaved off the solid support on treatment with trifluoroacetic acid in tetrahydrofuran providing α-alkylated or α,α′-bisalkylated ketones or were subjected to reductive cleavage with borane in tetrahydrofuran to give β-alkylated or β,β′-bisalkylated primary amines.
Formation, Alkylation, and Hydrolysis of Chiral Nonracemic <i>N</i>-Amino Cyclic Carbamate Hydrazones: An Approach to the Enantioselective α-Alkylation of Ketones
作者:Uyen Huynh、Stacey L. McDonald、Daniel Lim、Md. Nasir Uddin、Sarah E. Wengryniuk、Sumit Dey、Don M. Coltart
DOI:10.1021/acs.joc.8b00655
日期:2018.11.2
as α-functionalized ketones or derivatives thereof. We previously reported our preliminary studies on the development of a new enantioselective ketone α-alkylation procedure using N-amino cyclic carbamate (ACC) auxiliaries. In comparison to other auxiliary-based methods, ACC alkylation offers a number of advantages and is both highly enantioselective and high yielding. Herein, we provide a full account
Investigating<i>Saccharomyces cerevisiae</i>alkene reductase OYE 3 by substrate profiling, X-ray crystallography and computational methods
作者:Robert W. Powell, III、M. Pilar Buteler、Sunidhi Lenka、Michele Crotti、Sara Santangelo、Matthew J. Burg、Steven Bruner、Elisabetta Brenna、Adrian E. Roitberg、Jon D. Stewart
DOI:10.1039/c8cy00440d
日期:——
X-ray crystalstructures of unliganded and phenol-bound OYE 3 were solved to 1.8 and 1.9 Åresolution, respectively. Both structures were nearly identical to that of OYE 1, with only a single amino acid difference in the active site region (Ser 296 versus Phe 296, part of loop 6). Despite their essentially identical static X-ray structures, molecular dynamics (MD) simulations revealed that loop 6 conformations
ee up to virtually complete asymmetricinduction (99.5% ee). The acyclic ketones are transformed to their corresponding “SAMP-hydrazones” (S)-2 by reaction with the enantiomerically pure hydrazine (S)-l-amino-2-methoxymethyl-pyrrolidine [SAMP, (S)-1], readily available from (S)-proline. Metalation to form chiral azaenolates (S)-3 of EccZcn-configuration and then alkylation to product hydrazones 4 followed
描述了一种通用方法,该方法可使无环酮的整体对映选择性α-烷基化具有良好的总收率(44–86%,4步),对映选择性通常从> 94%ee到几乎完全不对称诱导(99.5%ee) )。通过与对映体纯的肼(S)-1-氨基-2-甲氧基甲基-吡咯烷[ SAMP,(S)-1 ]反应,将无环酮转化为相应的“ SAMP- azo”(S)-2来自(S)-脯氨酸。金属化形成E cc Z cn的手性氮杂酸酯(S)-3-构型,然后烷基化为产物4,然后在两相系统中通过甲硫氨酸9的酸性水解或臭氧分解裂解,可生成α-取代,对映体富集的无环酮5。在特殊情况下,当苯基直接连接到新生成的手性中心(5n,o,p)时,仅观察到低对映体过量。总结了17个示例,包括天然产物合成中的第一个应用(参见5abe和h)