Search results for " Synthesis"

Enantioselective synthesis of fluorinated alpha-amino acids and derivatives in combination with ring-closing metathesis: intramolecular pi-stacking i…

2001

[reaction: see text]. Hydride reduction of C=N bonds stereocontrolled by intramolecular pi-stacking interactions of 1-naphthylsulfinyl and N-aryl groups, nonoxidative Pummerer rearrangement, and ring-closing metathesis are efficiently combined in a highly stereoselective entry to enantiomerically pure cyclic and acyclic fluorinated beta-amino alcohols and alpha-amino acid derivatives, respectively.

Asymmetric Allylation/Ring Closing Metathesis: One-Pot Synthesis of Benzo-fused Cyclic Homoallylic Amines. Application to the Formal Synthesis of Ser…

2013

A one-pot asymmetric allylation/ring closing metathesis (RCM) sequence for the synthesis of cyclic homoallylic amines has been developed. A library of six- and seven-membered benzo-fused products has been synthesized in good yields and complete diastereoselectivity. The new methodology has been applied to the formal syntheses of the antidepressant Sertraline and the epimeric Norsertraline. The methodology is amenable for the synthesis of analogs.

Microwave-Assisted Tandem Organocatalytic Peptide-Coupling Intramolecular aza-Michael Reaction: α,β-UnsaturatedN-Acyl Pyrazoles as Michael Acceptors

2014

Conjugated N-acyl pyrazoles have been successfully employed in the organocatalytic enantioselective intramolecular aza-Michael reaction as ester surrogates. Bifunctional squaramides under microwave irradiation provided the best results in this transformation. Furthermore, this protocol has been combined with a peptide-coupling reaction in a tandem sequence. The final products were easily converted into the corresponding ethyl esters.

Stereoselective Synthesis of Microcarpalide

2002

The first total synthesis of the naturally occurring nonenolide, microcarpalide, is described. The key step in the synthesis was the ring-closing metathesis of a dienic ester prepared in turn by coupling an acid and an alcohol stereoselectively synthesized from (S,S)-tartaric acid and (R)-glycidol, respectively. [structure: see text]

Stereoselective Synthesis of the Cytotoxic Macrolide FD-891

2006

[reaction: see text] A total synthesis of the naturally occurring, cytotoxic macrolide FD-891 is described. Three fragments were first stereoselectively constructed using mainly asymmetric aldol and allylation reactions. The complete framework was then assembled using two Julia-Kocienski olefinations to connect the three fragments and a Yamaguchi reaction to close the macrolactone ring.

Stereoselective solid-phase synthesis of chiral piperidine derivatives by using an immobilized galactose auxiliary.

2003

Carbohydrate Scaffolds for Combinatorial Syntheses That Allow Selective Deprotection of All Four Positions Independent of the Sequence

2004

Biomimetic Synthesis of the Apoptosis-Inducing Thiazinoquinone Thiaplidiaquinone A

2012

A concise total synthesis of the apoptosis-inducing, marine metabolite thiaplidiaquinone A is described. The key ring forming steps are both based on biosynthetic considerations and involve the construction of the central benzo[c]chromene quinone unit by an extremely facile oxa-6π-electrocyclic ring closure reaction of an ortho-quinone intermediate, derived by tautomerization of a bis-benzoquinone, readily accessed from two simple phenolic precursors. This is followed by the installation of the 1,4-thiazine-dioxide ring by reaction of the benzo[c]chromene quinone with hypotaurine.

Recent Advances in Enantioselective Desymmetrizations of Prochiral Oxetanes

2021

Abstract Strain relief of oxetanes offers a plethora of opportunities for the synthesis of chiral alcohols and ethers. In this context, enantioselective desymmetrization has been identified as a powerful tool to construct molecular complexity and this has led to the development of elegant strategies on the basis of transition metal, Lewis acid, and Brønsted acid catalysis. This review highlights recent examples that harness the inherent reactivity of prochiral oxetanes and offers an outlook on the immense possibilities for synthetic application.

Design, synthesis and biological evaluation of novel stilbene-based antitumor agents

2008

A series of novel stilbene derivatives has been synthesized and studied with the main goal to investigate SAR of the amino compound 1a, as well as to improve its water solubility, a potentially negative aspect of the molecule that could be a serious obstacle for a pre-clinical development. We have obtained derivatives with good cytotoxic activity, in particular, the derivatives 5c and 6b could represent two novel leads for further investigation. Compound 8b, a morpholino-carbamate derivative, prodrug of 1a, has a very good solubility in water, and is active in suppressing growth of tumor cells at a concentration of 5000 nM, which is a concentration 100 times higher than the parent stilbene …