Chiral Ester Enolate Research Articles

ChemInform Abstract: Switchover of the Diastereofacial Selectivity in the Michael Reaction of a Chiral Ester Enolate with α,β‐Enone.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Switchover of the Diastereofacial Selectivity in the Michael Reaction of a Chiral Ester Enolate with α,β-Enone

Switchover of the Diastereofacial Selectivity in the Michael Reaction of a Chiral Ester Enolate with α,β-Enone

Synthesis, Conformational Analysis, and Biological Evaluation of Heteroaromatic Taxanes.

The asymmetric syntheses of heteroaromatic 3-[(tert-butyldimethylsilyl)oxy]-2-azetidinones 12-16 via chiral ester enolate-imine cyclocondensation chemistry are described. The azetidinones contain heteroaromatic moieties which, in certain cases, contribute to a decrease in enantioselectivity due to possible alternate coordinations in the transition states. The (3R,4S)-3-[(tert-butyldimethylsilyl)oxy]-4-heteroaryl-2-azetidinones were subsequently converted to the heteroaromatic taxanes 31-36 and 43-45. Conformational analyses of the 3'-(2-pyridyl) analogue 31 and 3'-(2-furyl) analogue 43 indicate they have solution conformational preferences virtually identical to paclitaxel and docetaxel. Heteroaromatic N-acyl paclitaxel analogues 47-51 were prepared from N-debenzoylpaclitaxel via Schotten-Baumann acylation. The majority of the 14 analogues displayed good to excellent activity in a microtubule assembly assay in comparison to paclitaxel. The analogues were also tested for cytotoxicity against B16 melanoma cells. 3'-Dephenyl-3'-(2-pyridyl)paclitaxel (31), 3'-dephenyl-3'-(2-furyl)paclitaxel (34), N-BOC-3'-dephenyl-3'-(2-furyl)paclitaxel (43), 3'-dephenyl-3'-(2-furyl)-N-(hexanoyl)paclitaxel (44), and N-debenzoyl-N-(3-furoyl)paclitaxel (51) were found to be more cytotoxic than paclitaxel against this cell line. 3'-Dephenyl-3'-(4-pyridyl)paclitaxel (33) and N-debenzoyl-N-(2-furoyl)paclitaxel (50) displayed cytotoxicity against B16 melanoma cells similar to paclitaxel.

Syntheses of new fluorine-containing taxoids by means of β-Lactam Synthon Method

A series of new fluorine-containing analogs of paclitaxel and docetaxel are synthesized using the coupling of (3 R,4 S)-1-acyl- β-lactams with high enantiomeric purity with properly protected baccatin III, 10-deacetylbaccatin III, and 14β-hydroxy-10-deacetylbaccatin III as the key step (β- Lactam Synthon Method). (3 R,4 S)-1-Acyl- β-lactams are prepared through efficient chiral ester enolate - imine cyclocondensation.

ChemInform Abstract: Creation of Chirality in the Reaction of the Chiral Ester Enolate‐ Imine Condensation Leading to the Stereodivergent Synthesis of β‐ Lactams.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A highly efficient route to taxotere by the β-Lactam Synthon Method

Taxotère, a highly promising anticancer drug, is synthesized through an efficient coupling of 7,10-diTroc-10-deacetylbaccatin III with enantiomerically pure (3R,4S)-1- tBOC-3-EEO- 4-phenylazetidin-2-one which is obtained via chiral ester enolate - imine cyclocondensation.

Asymmetric synthesis of β-lactams by chiral ester enolate - imine condensation

Asymmetric cyclocondensation of N,N-bis(silyl)glycinates bearing chiral ester moieties with aldimines is found to proceed with extremely high enantioselectivity to give the corresponding chiral β-lactams in good to high yields. It is found that the E/Z-geometry of the chiral ester-enolate ts responsible for cis/trans stereochemistry of the β-lactam formed. Effects of various chiral auxiliaries in the ester-enolates on the enantioselectivity of the reactions are examined.

ChemInform Abstract: Asymmetric (2,3)‐Wittig Rearrangement Involving a Chiral Ester Enolate Terminus. A Chiral Synthesis of erythro‐α‐Hydroxy‐β‐alkyl Carboxylic Acid Derivatives.

AbstractAsymmetric Wittig rearrangement of the optically active alkenyloxyacetates (I) yields predominantly the erythro‐derivatives (III), together with the threo‐carboxylates (IV).

Asymmetric [2,3]-Wittig Rearrangement Involving a Chiral Ester Enolate Terminus. A Chiral Synthesis of erythro-α-Hydroxy-β-alkyl Carboxylic Acid Derivatives

Abstract The title rearrangement of the (E-2-alkenyloxy)acetic esters derived from (−)-8-phenylmenthol has been shown to afford the corresponding 3-alkyl-2-hydroxy-4-pentenoic ester with an extremely high level of diastereoface selection (95–97% de) along with a high erythro selectivity (90–93%).