Stereoselective approach to pentenocins using RCM: synthesis of 6-epi-pentenocin B

The stereoselective synthesis of 6-epi-pentenocin B 3 is described using a stereoselective Grignard reaction and ring-closing metathesis (RCM) as the key steps.     

An efficient stereoselective synthesis of (+)-deoxoprosophylline

An efficient stereoselective synthesis of (+)-deoxoprosophylline from readily available p-anisaldehyde is described. Key steps in the synthesis include the stereoselective amination of anti-1,2-dibenzyl ether using chlorosulfonyl isocyanate, intermolecular olefination, and Pd-catalyzed intramolecular cyclization.     

Stereoselective Synthesis of β-Hydroxy- and β-Ethoxy-δ-lactones: Model Structures for Compounds Isolated from Otoba parvifolia

Abstract: In this paper we describe a very short stereoselective synthesis of the β-ethoxylactone 13, a model structure for compounds isolated from Otoba parvifolia. The method, which also produces β-hydroxy-esters and β-hydroxy-lactones, is based on a chemo- and stereoselective Reformatsky reaction.     

Stereoselective synthesis of the enantiomer of the key fragment of crocacin

A novel, stereoselective synthesis of the enantiomer of alcohol 5 is disclosed. The key steps of the synthesis include mercuric trifluoroacetate promoted regio- and stereoselective hydration of an α,β-unsaturated ester, Frater-alkylation and use of morpholine derived amide for acylation.     

Total synthesis of (−)-funebrine via Au-catalyzed regio- and stereoselective γ-butyrolactonization of allenylsilane

The stereoselective total synthesis of (−)-funebrine from 2-butyn-1-ol was described. The crucial steps in the synthesis involved the stereoselective enolate Claisen rearrangement of the (S)-α-acyloxy-α-alkynylsilane 8, the Au-catalyzed regio- and stereoselective lactonization of the allenylsilane 7, and the Paal-Knorr pyrrole condensation using an unsymmetrical 1,4-diketone 4b.     

The total synthesis of (±)-naphthyridinomycin. II. Construction of the pentacyclic carbon skeleton.

A synthesis of an advanced pentacyclic intermediate to the quinone antibiotic naphthyridinomycin (1) is described. The stereoselective synthesis of 2b from tricyclic lactam 3¹ features a regio- and stereoselective, intermolecular amidoalkylation reaction and a Friedel-Crafts ring closure to annelate the aromatic nucleus.     

Artificial intelligence designed drug synthesis: One-pot preparation of trans β-lactams and application to cholesterol absorption inhibitor SCH 47949 synthesis

An artificial intelligence designed SCH 47949 synthesis is achieved in a stereoselective manner. The key step contains a stereoselective one-pot construction of the trans β-lactam framework via thermal electrocyclization. N-arylation of the β-lactam ring system and a series of functional group transformations synthesized SCH 47949 in a reasonable chemical yield.     

Stereoselective Synthesis of the Decahydrofluorene Core of the Hirsutellones

A stereoselective synthesis of the decahydrofluorene core of the hirsutellones was accomplished in eight steps and in 43% overall yield. The key step of the synthesis is the highly stereoselective intramolecular Diels-Alder cyclization of the siloxacyclopentene-constrained tetraene 1.     

Stereoselective Synthesis of Trisubstituted Olefins

Abstract

A new method for the highly stereoselective synthesis of trisubstituted olefins is. presented. The method involves the stereoselective construction of various β-hydroxy phosphonamidates followed by their thermolysis to provide trisubstituted olefins in extremely high geometrical purity (>99/1).     

A stereocontrolled synthesis of (−)-detoxinine from l-ascorbic acid

A stereoselective synthesis of (−)-detoxinine, the core unit of the detoxifying agent detoxin D₁, is presented. The approach, characterized by the use of an inexpensive starting material and by the easy and stereoselective preparation of the key 4,5-disubstituted oxazolidin-2-one 11, proves to be a suitable alternative to the known procedures.     

The total synthesis of (±)-cycloeudesmol

The highly stereoselective total synthesis of (±)-cycloeudesmol was achieved by the stereoselective cyclopropane ring formation of an epoxy alcohol ($\text{7}$) as a key reaction.     

A concise and stereoselective synthesis of the brassinolide and related compounds’ side chains

A stereoselective synthesis of brassinolide, which involves construction of the side chain by highly stereoselective aldol reaction of 20S-6β-methoxy-3α,5-cyclo-5α-pregnane-20-carboxadehyde 5 with the anion of α-silyloxy ketone 6 is described.     

N-Functionalized 1-Alkynylamides: New Building Blocks for Transition Metal Mediated Inter- and Intramolecular [2+2+1] Cycloadditions

A conceptually new, stereoselective approach to compounds such as 1 and 2 is expected from the so far unknown class of N-functionalized 1-alkynylamides. Building blocks of the type I and II can be applied to inter- and intramolecular, regio- and stereoselective [Co₂(CO)₈]-mediated [2+2+1] cycloadditions.     

Novel construction of the brassinolide side chain

A stereoselective synthesis of brassinolide, which involves construction of the side chain by a highly stereoselective aldol reaction between 20S-6β-methoxy-3α,5-cyclo-5α-pregnane-20-carboxaldehyde 2 and ketone 3 or 4 catalyzed by l-proline, is described.     

First enantioselective synthesis of exiguamide,a nitrogen-containing spirocyclic sesquiterpene isolated from the marine sponge Geodia exigua

(+)-Exiguamide is a nitrogen-containing spirocyclic sesquiterpene isolated from the marine sponge Geodia exigua. This study aims to report the first synthesis of both enantiomers of exiguamide, featuring the stereoselective intramolecular cyclopropanation and stereoselective homoconjugate addition of azide to cyclopropyl ketone as the key steps.     

New reactions of alkynes with ketones in superbasic media

The present work reviews new reactions of alkynes with ketones in the superbasic media MOH—DMSO (M = Na, K, Cs) and KOBu^t—DMSO: the stereoselective nucleophilic addition of deprotonated ketones to the triple bond to form the E-isomers of β,γ-enones; vinylation of tertiary acetylenic alcohols that formed in situ from acetylene and ketones; the direct synthesis of vinyl ethers of tertiary acetylenic alcohols from acetylene and ketones; the stereoselective synthesis of dispirocyclic ketals containing the Z-ethylene fragment from arylalkynes and two molecules of a cyclic ketone; the stereoselective cascade synthesis of hexahydroazulenones from two arylalkyne molecules and 2-alkylcyclohexanones; the stereoselective cascade assembly of 7-methylidene-6,8-dioxabicyclo[3.2.1]octanes from two acetylene molecules and two ketone molecules; the stereoselective cascade synthesis of 7-methylidene-6,8-dioxabicyclo[3.2.1]octanes from acetylenes and 1,5-diketones; and the three-component cascade reaction of acetylene, ketones, and oximes to afford 4-methylidene-3-oxa-1-azabicyclo-[3.1.0]hexanes.     

2-Isopropylbenzimidazole and 2-methylbenzimidazole as bulky proton sources: Stereoselective protonation and application to the synthesis of γ- and δ-lactones

2-Isopropylbenzimidazole and 2-methylbenzimidazole have been found to be effective bulky proton sources for stereoselective protonation of chiral enolate anions. 2-Isopropylbenzimidazole worked in the stereoselective protonation of the Birch reduction of chiral α,β-unsaturated imides. On the other hand, 2-methylbenzimidazole was found to be the best protonation reagent in the isomerization reaction of α,β-unsaturated imide into β,γ-unsaturated imide. The Birch reduction using 2-isopropylbenzimidazole realized a concise and stereoselective synthesis of δ-lactone 14, a sex pheromone of Macrocentrus grandii, while the isomerization reaction using 2-methylbenzimidazole was employed in the highly stereoselective synthesis of the γ-lactone intermediate in the synthesis of depsipeptide antibiotics. These bulky proton sources would be powerful tools to achieve a concise synthesis of natural products.     

An asymmetric synthesis of (+)-desoxoprosophylline

An efficient synthesis of (+)-desoxoprosophylline is described. The key steps in the reaction sequence include the preparation of an N-Cbz-sulfilimine from the corresponding sulfoxide using the Burgess reagent, regio- and stereoselective hetero-functionalization of an alkene using the pendant sulfilimine as the nucleophile and a stereoselective amidomercuration to form the cis-2,6-disubstituted piperidine ring.     

Highly stereoselective Friedel-Crafts type cyclization. Facile access to enantiopure 1,4-dihydro-4-phenyl isoquinolinones

The present report describes a stereoselective synthesis of 1,4-dihydro-4-phenyl isoquinolinones 5 based on a stereoselective Friedel-Crafts type cyclization. Cyclization precursors 1 were prepared in two steps, from the readily available (S)-mandelic acid, in 60-80% overall yield. The stereoselective electrophilic cyclization was accomplished in 20-86% yield and with 20-97% ee. In the course of this work, the presence of the amide carbonyl was found to be particularly important to guarantee a stereospecific process during the electrophilic aromatic substitution.     

Facile Method for Stereoselective Synthesis of New Chiral (1R,4aR,8aR)‐1,3,4,4a,5,7,8,8a‐Octahydro‐2‐methylene‐naphthalene‐6‐one‐1‐propanenitrile,an Important Precursor of Solanapyrones

A novel and facile strategy for stereoselective synthesis of new chiral (1R,4aR,8aR)‐1,3,4,4a,5,7,8,8a‐octahydro‐2‐methylenenaphthalene‐6‐one‐1‐propanenitrile (8) by one‐pot stereoselective hydrogenation/acetalization and Beckmann fragmentation is described. Chiral octalone 8, an important precursor of solanapyrone, was obtained in good yield.