0000000001301071
AUTHOR
J. Murga
Double Diastereoselection in Aldol Reactions Mediated by Dicyclohexylchloroborane between Chiral Aldehydes and a Chiral Ethyl Ketone Derived from l-Erythrulose. Synthesis of a C1−C9 Fragment of the Structure of the Antifungal Metabolite Soraphen A1α
Both matched and mismatched diastereoselections have been observed in the aldol reactions of a range of chiral aldehydes with the dicyclohexylboron enolate of a chiral ethyl ketone related to l-erythrulose. As was previously observed in the corresponding aldol reactions with l-erythrulose derivatives, the Felkin−Anh model provides an adequate explanation for the stereochemical outcome of reactions with chiral α-methyl aldehydes. However, a satisfactory account of the results observed with α-oxygenated aldehydes was only possible with the Cornforth model. As a practical application of the methodology described herein, a C1−C9 fragment of the structure of the antifungal macrolide soraphen A1α…
On the structure of passifloricin A: asymmetric synthesis of the delta-lactones of (2Z,5S,7R,9S,11S)- and (2Z,5R,7R,9S,11S)tetrahydroxyhexacos-2-enoic acid.
Stereoselective syntheses of the delta-lactone of (2Z,5S,7R,9S,11S)-tetrahydroxyhexacos-2-enoic acid, the structure reported for passifloricin A, and of its (5R)-epimer are described. The creation of all stereogenic centers relied upon Brown's asymmetric allylation methodology. The lactone ring was created via ring-closing metathesis. The NMR data of both synthetic products, however, were different from those of the natural product. The published structure of passifloricin A is thus erroneous and will require further synthetic work to be unambiguously assigned. [structure: see text]
Stereoselective Total Synthesis and Absolute Configuration of the Natural Decanolides (−)-Microcarpalide and (+)-Lethaloxin. Identity of (+)-Lethaloxin and (+)-Pinolidoxin
[reaction: see text] Convergent, stereoselective syntheses of the pharmacologically active, naturally occurring lactones (-)-microcarpalide and (+)-lethaloxin have been achieved from the commercially available, chiral reagents (R)-glycidol, (S,S)-tartaric acid, and d-ribose as the starting materials. These syntheses have further served to establish the hitherto unknown absolute configuration of (+)-lethaloxin and to show its identity with (+)-pinolidoxin.
Stereoselective Synthesis and Structural Correction of the Naturally Occurring Lactone Stagonolide G
A convergent synthesis of the structure proposed for the naturally occurring lactone stagonolide G is described. All three stereocenters were created with the aid of asymmetric Brown allylations. The lactone ring was built by means of a ring-closing metathesis (RCM). The synthetic and the natural compound differed in their spectral properties. A new structure is now proposed for stagonolide G and demonstrated by means of a chemical transformation.
Lung tumorspheres as a drug screening platform against cancer stem cells.
Treatment resistance and metastasis are linked to cancer stem cells (CSCs). This population represents a promising target, but remains unexplored in lung cancer. The main objective of this study was to characterize lung CSCs and discover new therapeutic strategies.
2.14 Selected Diastereoselective Reactions: Enolate Alkylation
This chapter discusses processes in which enolates are subjected to reaction with alkylating reagents. In all the processes examined here, at least one of the two reaction components is chiral and the reaction gives rise to one or more diastereomeric compounds. In most cases, the enolate is generated through deprotonation of the corresponding carbonyl precursor with a suitable base, but in several cases, the enolate is generated differently, for example, through Michael addition of a nucleophile to a conjugated carbonyl compound. The various factors that have been found to influence the stereochemical outcome of the alkylation reaction in a measurable way are also discussed. The material ha…
An ab initio study of the enolboration of 3-pentanone mediated by boron monochlorides L2BCl
Abstract Using ab initio methods at the HF/6-31G∗∗ level, we have studied the mechanism of the enolboration of 3-pentanone mediated by boron monochlorides L2BCl (L=H, methyl and isopropyl) and trimethyl amine. The size of the L group has been found to have a decisive influence on the configuration (E or Z) of the formed boron enolate. Thus, whereas our calculations predict that dimethylboron chloride yields the Z enolate with high stereoselectivity, diisopropylboron chloride is found to yield predominantly the E enolate. The difference in behavior is due mainly to steric features related to the conformational bias of the respective ketone–boron chloride complexes formed reversibly in the fi…
Double diastereoselection in aldol reactions mediated by dicyclohexylchloroborane between L-erythrulose derivatives and chiral aldehydes. The Felkin-Anh versus Cornforth dichotomy.
Both matched and mismatched diastereoselections have been observed in aldol reactions of the B,B-dicyclohexylboron enolate of a protected l-erythrulose derivative with a range of chiral aldehydes. The stereochemical outcome of reactions with alpha-methyl aldehydes can be adequately explained within the Felkin-Anh paradigm. In the case of alpha-oxygenated aldehydes, however, strict adherence to this model does not allow for a satisfactory account of the observed results. In such cases, the Cornforth model provides a much better explanation.
CCDC 148163: Experimental Crystal Structure Determination
Related Article: M.Carda, R.Portoles, J.Murga, S.Uriel, J.A.Marco, L.R.Domingo, R.J.Zaragoza, H.Roper|2000|J.Org.Chem.|65|7000|doi:10.1021/jo0009651
CCDC 148166: Experimental Crystal Structure Determination
Related Article: M.Carda, R.Portoles, J.Murga, S.Uriel, J.A.Marco, L.R.Domingo, R.J.Zaragoza, H.Roper|2000|J.Org.Chem.|65|7000|doi:10.1021/jo0009651
CCDC 271535: Experimental Crystal Structure Determination
Related Article: J.Garcia-Fortanet, J.Murga, E.Falomir, M.Carda, J.A.Marco|2005|J.Org.Chem.|70|9822|doi:10.1021/jo051353p
CCDC 148164: Experimental Crystal Structure Determination
Related Article: M.Carda, R.Portoles, J.Murga, S.Uriel, J.A.Marco, L.R.Domingo, R.J.Zaragoza, H.Roper|2000|J.Org.Chem.|65|7000|doi:10.1021/jo0009651
CCDC 210749: Experimental Crystal Structure Determination
Related Article: J.A.Marco, M.Carda, S.Diaz-Oltra, J.Murga, E.Falomir, H.Roeper|2003|J.Org.Chem.|68|8577|doi:10.1021/jo035159j
CCDC 269222: Experimental Crystal Structure Determination
Related Article: S.Diaz-Oltra, J.Murga, E.Falomir, M.Carda, G.Peris, J.A.Marco|2005|J.Org.Chem.|70|8130|doi:10.1021/jo051307p
CCDC 620478: Experimental Crystal Structure Determination
Related Article: P.Alvarez-Bercedo, J.Murga, M.Carda, J.A.Marco|2006|J.Org.Chem.|71|5766|doi:10.1021/jo060314q
CCDC 269772: Experimental Crystal Structure Determination
Related Article: S.Diaz-Oltra, J.Murga, E.Falomir, M.Carda, G.Peris, J.A.Marco|2005|J.Org.Chem.|70|8130|doi:10.1021/jo051307p
CCDC 223372: Experimental Crystal Structure Determination
Related Article: J.Murga, P.Ruiz, E.Falomir, M.Carda, G.Peris, J.A.Marco|2004|J.Org.Chem.|69|1987|doi:10.1021/jo0356356
CCDC 148165: Experimental Crystal Structure Determination
Related Article: M.Carda, R.Portoles, J.Murga, S.Uriel, J.A.Marco, L.R.Domingo, R.J.Zaragoza, H.Roper|2000|J.Org.Chem.|65|7000|doi:10.1021/jo0009651
CCDC 617560: Experimental Crystal Structure Determination
Related Article: J.Garcia-Fortanet, J.Murga, M.Carda, J.A.Marco|2006|Org.Lett.|8|2695|doi:10.1021/ol060669w