Enantioselective Synthesis of syn/anti-1,3-Amino Alcohols via Proline-Catalyzed Sequential α-Aminoxylation/α-Amination and Horner−Wadsworth−Emmons Olefination of Aldehydes

Synthesis of enantioenriched α-heteroatom functionalised aldehydes by chiral organocatalysis and their synthetic applications

Asymmetric organocatalysis is a versatile method for the enantioselective α-functionalisation of aldehydes. The synthetic scope for chiral α-heteroatom substituted aldehydes is examined including their applications in synthesis.

trans-Diastereoselective Syntheses of γ-Lactones by Visible Light-Iodine-Mediated Carboesterification of Alkenes

This study aims to develop an intermolecular lactonization reaction of alkenes with carbonyls mediated by visible light and molecular iodine. The one-step reaction involved the carboesterification of alkenes to produce the corresponding lactones in moderate to good yield. It was also revealed that it is possible to control the diastereoselectivity of the reaction by altering the base used and the reaction conditions. When water was added as a solvent, the reaction resulted in the formation of lactones with trans-selectivity. A mechanistic investigation was undertaken and it was found that the reaction requires the generation of an iodine radical from molecular iodine, driven by visible light irradiation, and proceeds via the formation of an iodine radical alkene adduct. The proposed reaction is an example of a rare-metal free intermolecular addition cyclization reaction, which is an environment-friendly chemical process that only uses molecular iodine. In addition, since diastereoselectivity was observed without the use of any specific reagents, the developed methodology is an example of a novel stereoselective transformation using only cost-effective reagents.

Ring-locking strategy facilitating determination of absolute optical purity of 2-amino-1-butanol by reverse-phase high-performance liquid chromatography

A concise and efficient reverse-phase high-performance liquid chromatography (RPLC) method has been established for absolute optical purity assay of 2-amino-1-butanol, which is an important synthetic intermediate of various drugs.

Diastereoselective synthesis of furanose and pyranose substituted glycine and alanine derivatives via proline-catalyzed asymmetric α-amination of aldehydes

A concise organocatalytic route toward the synthesis of furanose and pyranose substituted glycine and alanine derivatives is reported. These compounds are core structural units of some of the naturally available antibiotics and antifungal agents. Proline-catalyzed asymmetric α-amination of aldehydes derived from sugars is used as the key reaction to synthesize twelve sugar amino acid derivatives. The asymmetric transformations proceeded in good yields and with good to excellent diastereoselectivity. The application of the synthesized amino acids is demonstrated by synthesizing a tripeptide containing one of them.

Total synthesis of (−)-(6R,11R,14S)-colletallol via proline catalyzed α-aminoxylation and Yamaguchi macrolactonization

A simple and efficient synthesis of 14-membered macrolide (−)-(6R,11R,14S)-colletallol was achieved in a highly diastereoselective manner using proline catalyzed alpha-aminoxylation and Yamaguchi protocol.

Asymmetric Aldol-Tishchenko Reaction of Sulfinimines

Methods for the preparation of 1,3-amino alcohols and their derivatives containing two stereogenic centers usually involve a two-step installation of the chiral centers. An aldol-Tishchenko reaction of chiral sulfinimines which involves the first reported reduction of a C═N in this type of reaction is described. Two and even three chiral centers can be installed in one synthetic step, affording anti-1,3-amino alcohols in good diastereo- and enantioselectivity.

Analysis of relationship between oxidized phospholipid structure and interaction with the class B scavenger receptors

Recognition of specific oxidized phospholipids oxPCCD36 by scavenger receptors CD36 and SR-BI plays a critical role in several pathophysiological processes. The structural basis for the recognition of oxPCCD36 by CD36 and SR-BI is poorly understood. We describe here the design and synthesis of a series of model oxidized phospholipids having various functional groups at sn-1, sn-2, and sn-3 positions. Synthetic methodologies and experimental details for the preparation of specific examples of model oxidized phospholipids are presented. The correlation between their structure and their ability to serve as ligands for CD36 and SR-BI was determined using competitive binding assay on cells overexpressing scavenger receptors, direct binding assay to scavenger receptors expressed as GST-fusion proteins, and cholesterol ester synthesis assay using mouse peritoneal macrophages.

Divergent synthesis of various iminocyclitols from d-ribose

A very efficient route to the diastereoselective synthesis of polyhydroxy pyrrolidines, piperidines and azepanes from an aldehyde derivative of ribose is reported.

A stereocontrolled synthesis of Hagen's gland lactones via iterative proline catalyzed α-aminoxylation and oxa-Michael addition reactions

A simple and efficient synthesis of Hagen's gland lactones was achieved using a sequential α-aminoxylation/oxa-Michael approach in a highly diastereoselective manner with assignment of relative configurations.

A stereoselective approach to indolizidine and pyrrolizidine alkaloids: total synthesis of (−)-lentiginosine, (−)-epi-lentiginosine and (−)-dihydroxypyrrolizidine

The total synthesis of (−)-lentiginosine, epi-1,2-lentiginosine and dihydroxypyrrolizidine is reported from an aldehyde as a starting material using organocatalysis and asymmetric dihydroxylation as key steps.

Preparation of α-imino aldehydes by [1,3]-rearrangements of O-alkenyl oximes

The synthesis of α-imino aldehydes has been achieved through the thermal [1,3]-rearrangement of O-alkenyl benzophenone oximes. A copper-mediated C-O bond coupling between benzophenone oxime and alkenyl boronic acids provides facile access to the required O-alkenyl oximes and a Horner-Wadsworth-Emmons olefination can be applied to the α-imino aldehyde products to give γ-imino-α,β-unsaturated esters. The scope of the method is described and mechanistic experiments are discussed.

Total synthesis of sedum alkaloids via catalyst controlled aza-Cope rearrangement and hydroformylation with formaldehyde

The catalytic asymmetric aminoallylation of chiral aldehydes is developed as a new method for the catalyst controlled synthesis of syn- and anti-1,3-aminoalcohols. This methodology is highlighted in the synthesis of the sedum alkaloids (+)-sedridine and (+)-allosedridine both of which have their final carbon incorporated during closure of the piperidine ring via a hydroformylation with formaldehyde.

Enantio- and diastereocontrolled conversion of chiral epoxides to trans-cyclopropane carboxylates: application to the synthesis of cascarillic acid, grenadamide and L-(-)-CCG-II

An efficient high yielding improved method for the enantio- and diastereoselective cyclopropanation of chiral epoxides using triethylphosphonoacetate and base (Wadsworth-Emmons cyclopropanation) is reported. The utility of this protocol is illustrated by concise and practical synthesis of cascarillic acid, grenadamide and L-(-)-CCG-II, a cyclopropane containing natural products.

Aminohydroxyacetone synthons: versatile intermediates for the organocatalytic asymmetric aldol reaction

A practical method for the synthesis of 1,3-aminohydroxyacetone synthons was developed, and their utility in the organocatalytic asymmetric aldol reaction was demonstrated in a short synthesis of aza-sugars.

One-pot stereoselective synthesis of 1,2-amino alcohol derivatives

Common β-hydroxy amino acids (such as threonine) can be readily transformed into 1,2-amino alcohols with excellent stereoselectivity. This one-pot decarboxylation-alkylation process allows the replacement of the carboxyl group by alkyl, allyl, or aryl groups, generally in high yields. A variation of the process (decarboxylation-Diels-Alder) allows the formation of bi- and polycyclic systems, which are useful precursors of alkaloid cores or iminosugars.