The aldol reaction is one of the most important methods for the stereoselective construction of polyketide natural products, not only for nature but also for synthetic chemistry. The tremendous development in the field of aldol additions during the last 30 years has led to more and more total syntheses of complicated natural products. This Review illustrates by means of selected syntheses of natural products the new variants of the aldol addition. This includes aldol additions with various metal enolates, as well as metal-complex-catalyzed, organocatalytic, and biocatalytic methods.

Modern aldol methods for the total synthesis of polyketides.

While natural and synthetic N-nucleosides are vulnerable to enzymatic and acid-catalyzed hydrolysis of the nucleosidic bond, their C-analogues are much more stable. Several C-nucleosides are naturally occurring compounds, e.g., pseudouridine (isolated from the yeast t-RNA) and showdomycin (an antibiotic). Development of novel synthetic methodologies allowed the preparation of a large variety of synthetic analogues, which found numerous applications in medicinal chemistry and chemical biology. Most important biologically active C-nucleosides are the inhibitors of purine nucleosides phosphorylase or IMP dehydrogenase. A number of artificial aryl-C-nucleosides capable of π-stacking are being vigorously investigated as building blocks in chemical biology. In the past few years, several Artificial Expanded Genetic Information Systems (AEGIS)1 have been successfully developed as prime examples of synthetic biology, a newly emerging interdisciplinary area, with the ultimate goal to design systems where high-level behaviors of the living matter are mimicked by artificial chemical systems.2,3

C-nucleosides: synthetic strategies and biological applications.

Enantio- and diastereoselective aldol reactions of achiral ethyl and methyl ketones with aldehydes: the use of enol diisopinocampheylborinates

A directed cross-aldol reaction of silyl enol ethers with carbonyl compounds, such as aldehydes and ketones, promoted by a Lewis acid, a reaction which is now widely known as the Mukaiyama aldol reaction. It was first reported in 1973, and this year marks the 40th anniversary. The directed cross-aldol reactions mediated by boron enolates and tin(II) enolates also emerged from the Mukaiyama laboratory. These directed cross-aldol reactions have become invaluable tools for the construction of stereochemically complex molecules from two carbonyl compounds. This Minireview provides a succinct historical overview of their discoveries and the early stages of their development.

The Mukaiyama aldol reaction: 40 years of continuous development.

Extraction of lithium with functionalized lithium ion-sieves

New borylating reagents, (Bu2BOTf and 9-BBNOTf), were prepared in high yields. The triflates reacted with enolizable ketones in the presence of tertiary amines to generate selectively one of the regioisomers of vinyloxyboranes by the choice of the reagents (the dialkylboryl triflates and tertiary amines) under mild reaction conditions. Vinyloxyboranes thus generated showed remarkable reactivity toward aldehydes to give only one regioisomer of the corresponding cross-aldols in good yields. High stereoselectivity was also observed in these reactions.

Regio- and stereoselective cross-aldol reactions via dialkylboryl triflates.

A new synthesis of cross-aldols from two different carbonyl compounds by using di-n-butylboryl trifluoromethanesulfonate and tertiary amine is described In the case of methyl ketones, the reaction takes place in regiospecific manner to afford the corresponding aldols in good yields

NEW CROSS-ALDOL REACTION Via VINYLOXYBORANES

A directed cross-aldol reaction between two different carbonyl compounds by using 9-trifluoromethylsulfonyl-9-borabicyclo[3.3.1]nonane and tertiary amine is described. The reaction of methyl ketones with the other carbonyl compounds takes place in regiospecific manner to afford the corresponding cross-aldols in good yields through intermediates, 9-(1-methyl-1-alkenyl)oxy-9-borabicyclo[3.3.1]nonanes.

New directed cross-aldol reaction using 9-trifluoromethylsulfonyl-9-borabicyclo[3.3.1]nonane

Showdomycin was prepared in excellent overall yield using 1,2-bis(trimethylsiloxy)cyclobut-1-ene for the construction of the maleimide unit of the molecule.

Highly efficient method for the synthesis of showdomycin

Reaction des α-trimethylsilyl alcanones avec des aldehydes et des acetals d'aldehydes en presence de SnCl 4 ou BF 3 -diethylether, ou en presence de diisopropylamidure de lithium

Tan Inoue

Papers

Regio- and stereoselective cross-aldol reactions via dialkylboryl triflates.

NEW CROSS-ALDOL REACTION Via VINYLOXYBORANES

New directed cross-aldol reaction using 9-trifluoromethylsulfonyl-9-borabicyclo[3.3.1]nonane

Highly efficient method for the synthesis of showdomycin

Aldol reactions with a .alpha.-trimethylsilyl ketones. Dual roles of the trimethylsilyl group for regiospecific generation of enolate equivalents