Enantiodivergent total synthesis of microcarpalide from l-tartaric acid

γ-Hydroxy Amides from Tartaric Acid: Versatile Chiral Building Blocks for the Total Synthesis of Natural Products

"Chiral pool" compounds possessing well defined stereocenters and suitable functionality serve as excellent building blocks for the synthesis of natural products and therapeutically important compounds. Tartaric acid is a C₂ -symmetric molecule available in both enantiomeric forms. It was extensively utilized in the synthesis of privileged chiral ligands/catalysts such as TADDOLs, and as a start point in the synthesis of plethora of compounds. The advent of several new C-C bond forming reactions offers opportunity for the development of novel synthetic strategies based on chiral pool compounds. We found that the desymmetrization of the bis-dimethyl amide/Weinreb amide derived from tartaric acid can be accomplished by controlled addition of Grignard /organolithium reagents leading to the mono keto amides, the reduction of which affords the γ-hydroxy amides. This account describes our research efforts of more than a decade on the synthesis and application of diverse γ-hydroxy amides derived from tartaric acid in the total synthesis of structurally simple to complex bio-active natural products.

Stereodivergent routes in organic synthesis: marine natural products, lactones, other natural products, heterocycles and unnatural compounds

Enantio- and diastereodivergent routes to marine-origin natural products with different sizes of cyclic ethers and lactones have been used in order to assign stereochemical features. Kainoid amino acids such as isodomoic acids have been synthesized using diastereodivergent routes. The bis(indole) alkaloid dragmacidin F has been prepared by enantiodivergent strategies as well as furanoterpenes and the tetracyclic agelastatin A. Natural products containing five-membered lactones like quercus lactones, muricatacins, goniofufuranones, methylenolactocins and frenolicin B have been synthesized using stereodivergent routes. Macrolides are very abundant lactones and have been mainly prepared from the corresponding seco-acids by lactonization, such as lasiodiplodin, zaeralanes, macrosphelides and haloprins, or by ring-closing metathesis, such as aspercyclides, microcarpalides, macrolides FD-891 and 892, and tetradic-5-en-9-olides. Other natural products including cyclic ethers (such as sesamin, asarinin, acetogenins, centrolobines and nabilones), alcohols (such as sulcatol), esters (such as methyl jasmonates), polycyclic precursors of fredericamycin, amino alcohols (such as ambroxol and sphingosines), isoprostanes, isofurans, polyketide precursors of anachelins, brevicomins, gummiferol, shikimic acid and the related compounds, and the pheromone disparlure have been synthesized stereodivergently. Heterocyclic systems such as epoxides, theobroxides and bromoxones, oxetan-3-ones, 5- to 8-membered cyclic ethers, azetidones, γ-lactams, oxazolidinones, bis(oxazolines), dihydropyridoisoindolines and octahydroisoquinolines have been prepared following stereodivergent routes. Stereodivergent routes to unnatural compounds such as alkenes, dienes, allenes, cyclopropanes, alcohols, aldols, amines, amino alcohols, β-amino acids, carboxylic acids, lactones, nitriles and α-amino nitriles have been considered as well.

A ring closing metathesis strategy for carbapyranosides of xylose and arabinose

The synthesis of β-carba-xylo and arabino pyranosides of cholestanol is described. The synthetic strategy, which is analogous to the Postema approach to C-glycosides, centers on the ring closing metathesis of an enol ether-alkene precursor to give a cyclic enol ether that is elaborated to a carba-pyranoside via hydroboration-oxidation on the olefin. The method, which is attractive for its modularity and stereoselectivity, may find wider applications to carba-hexopyranosides and other complex cycloalkyl ether frameworks.

A ring closing metathesis strategy for carbapyranosides of xylose and arabinose

The synthesis of β-carba-xylo and arabino pyranosides of cholestanol is described. The synthetic strategy, which is analogous to the Postema approach to C-glycosides, centers on the ring closing metathesis of an enol ether-alkene precursor to give a cyclic enol ether that is elaborated to a carba-pyranoside via hydroboration-oxidation on the olefin. The method, which is attractive for its modularity and stereoselectivity, may find wider applications to carba-hexopyranosides and other complex cycloalkyl ether frameworks.