The wittig reaction of non-stabilized phosphorus ylides and aromatic aldehydes. Studies on erythro and threo β-hydroxyphosphonium salts and the promotion of stereochemical drift by synergism between diastereomers

In deprotonation studies with isomerically pure $\text{erythro}$-3 and $\text{threo}$-3, “retro-Wittig” reaction was only detected for $\text{erythro}$-3. Mixtures of $\text{erythro}$-3 and $\text{threo}$-3, under lithium salt-free conditions, undergo stereochemical drift because of synergism between diastereomeric oxaphosphetanes $\text{cis}$-2 and $\text{trans}$-2 during their decomposition to alkenes.     

Synthesis of both 2,3-erythro- and 2,3-threo- isomers of aplidiasphingosine,a bioactive marine terpenoid

2,3-$\text{threo}$- and 13,14-$\text{erythro}$-Relative configurations were proposed for aplidiasphingosine by synthesizing both its 2,3-erythro- and 2,3-$\text{threo}$- isomers and examining their ¹³c-NMR spectra.     

Enantio- and diastereomerically pure threo-homoallylic alcohols via highly stereoselective reduction of α-methyl-β,γ-unsaturated ketones

Reduction of α-methyl-β,γ-unsaturated ketones with L-Selectride proceeded with high $\text{threo}$-selectivity to afford $\text{threo}$-β-methyl homoallylic alcohols of high enantio- and diastereomerical purities.     

Stereoselective synthesis of β-hydroxy-α-methylketones via z- and e-vinyloxyboranes generated directly from cyclohexyl ethyl ketone

$\text{E}$- and $\text{Z}$-dialkylvinyloxyboranes, prepared directly from cyclohexyl ethyl ketone, undergo stereo-selective aldol condensations to provide $\text{threo}$- $\text{erythro}$-β-hydroxy-α-methylketones, respectively.     

Stereoselective synthesis of β-hydroxy-α-methylcarboxylic acid thiol esters via vinyloxyboranes

Both $\text{threo}$- and $\text{erythro}$-β-hydroxy-α-methylcarboxylic acid thil esters are stereoselectively synthesized through an aldol-type condensation of vinyloxyboranes derived formally from s-$\text{tert}$-butyl propanethioate.     

Diastereoselection in the reactions of thioallylic anions with benzaldehyde

Reactions of the anions of (Z)-2-alkenyl N,N-dimethyldithiocarbamates with benzaldehyde gave the $\text{erythro}$ isomers of 4-hydroxy-4-phenyl-(E)-1-alkenyl N,N-dimethyldithiocarbamates stereoselectively and those of the anions of (E)-2-alkenyl N,N-dimethyldithiocarbamates afforded the $\text{threo}$ isomers predominantly.     

Synthesis of (+)-galantinic acid,a constituent amino acid in the peptide antibiotic galantin I, via the stereoselective epoxidation of a chiral serine equivalent

Epoxidation of (2$\text{R}$)-$\text{t}$-butoxycarbonylamino-3-butenol afforded, in a highly stereo-selective manner, a $\text{threo}$-3,4-epoxy-2-aminobutanol derivative which was successfully converted to the unusual amino acid (+)-galantinic acid in 8 steps $\text{via}$ regiospecific epoxide ring opening with divinyl cuprate.     

Stereochemistry of bis-(dichlorocyclopropanation) and -(epoxidation) of 1,4-diarylbutadienes

Dichlorocyclopropanation as well as epoxidation of the 1,4-diarylbutadienes $\text{1}$-$\text{4}$ to give the mono- and/or bisadducts according to several hindrance of large substituents as 2,6-dichlorophenyl. The bisadducts are formed preferably as $\text{meso}$- (or $\text{threo}$-) isomers.     

Stereoselective conversion of allylic alcohols to n-acyl-trans-4,5-dialkyloxazolidines.

The stereoselective synthesis of N-acyl-$\text{trans}$-4,5-dialkyloxazolidines (precursors to $\text{threo}$-β-amino alcohols) through a procedure involving amidomethylation of a 2° allylic alcohol followed by mercuric-ion inititated cyclofunctionalization is reported.     

Stereochemistry of the reactions of β-halothioethers with NaCN and AgCN

The S_N reactions of NaCN and AgCN with $\text{erythro}$ and $\text{threo}$-2-methylthio-3-halobutanes are reported. The stereochemistry of the resulting nitriles and isonitriles demonstrates that total retention in configuration has taken place in these processes. This disagrees with the accepted explanation for the regioselectivity of these reactions.     

Synthesis of erythro- and threo-α-bromo-α′-fluorosuccinic acids

$\text{erythro}$- and $\text{threo}$-α-Bromo-α′-fluorosuccinic acids have been prepared from their corresponding dimethyl esters. Because of the extreme readiness of elimination of hydrogen fluoride in basic medium, a special method of acid hydrolysis had to be applied. Hydrogen and fluorine NMR spectra are reported.     

Biosynthesis of tuberin and xanthocillin from tyrosine

(2S)-Tyrosine (5) is incorporated stereospecifically into tuberin (1) with retention of the 3-$\text{pro}$-S proton and incomplete retention of the 2-S proton; a parallel pathway to the xanthocillin (4) is apparent with stereospecific retention of the 3-$\text{pro}$-R proton of tyrosine; results of experiments with $\text{threo}$- and $\text{erythro}$-3-hydroxytyrosine in relation to tuberin biosynthesis are reported.     

Stereocontrolled addition to a penaldic acid equivalent: an asymmetric of threo-β-hydroxy-L-glutamic acid

The asymmetric synthesis of $\text{threo}$-β-hydroxy-L-glutamic acid (7) via a stereo-selective addition to the chiral penaldic acid equivalent 3 is described.     

The effect of environment on the reactions of thiiranium ions

The thiiranium ion formed by the reaction of $\text{Z}$-1-phenylpropene and (4-ClC₆H₄S)₂SC₆H₄ClSbCl₆ in CH₂Cl₉ at ?70°C reacts with Cl^? to form both $\text{erythro}$- and $\text{threo}$-Markownikoff B-chlorosulfides.     

Reversal of diastereofacial selectivity in the intramolecular michael addition of -α-carbamoyloxy-α,β-unsaturated esters. Synthesis of N-benzoyl-D,L-daunosamine

Contrary to the precedents, 1,3-anti stereoselection was found in the intramolecular Michael addition of ethyl $\text{threo}$,5-carbamoyloxy-4-trialkylsilyloxy-2-hexenoate to culminate in a synthesis of N-benzoyl-$\text{D}$,$\text{L}$-daunosomine. The antiperiplanar effect due to the group at 4-position was revealed to play a major role in the stereoselection in this type of reactions. N-benzoyl-$\text{D}$,$\text{L}$-3-epidaunosamine was also synthesized by 1,2-syn asymmetric induction.     

Direct synthesis of the antitumor agent erythro-α-amino-3-bromo-4,5-dihydroisoxazole-5-acetic acid

Generation of bromonitrile oxide in the presence of vinylglycine leads to the formation of the title compound $\text{2}$ and its $\text{threo}$ isomer in good yield.     

Determination of the absolute configuration at C-6 and C-7 of serricornin (4,6-dimethyl-7-hydroxy-3-nonanone), the sex pheromone of the cigarette beetle

The absolute configuration at C-6 and C-7 of serricornin was established as (6$\text{S}$, 7$\text{S}$) by synthesizing its (6$\text{R}$, 7$\text{S}$-$\text{erythro}$ and (6$\text{R}$, 7$\text{R}$-$\text{threo}$ isomers.     

Heteroatom directed β-lithiation of a vinyl ether

Oxygen directed β-deprotonation of a vinyl ether leads to $\text{Z}$ substituted enol ethers. The stereoselective elaboration to a naturally occuring $\text{threo}$ 1,3-diol is described.     

Elimination of hydrogen fluoride from fluorinated succinic acids. (III) kinetics of dehydrofluorination of erythro- and threo-α-bromo-α′-fluorosuccinic acids

Treatment of $\text{erythro}$- and $\text{threo}$-α-bromo-α′-fluorosuccinic acids with aqueous alkali results in the elimination of hydrogen fluoride in preference to hydrogen bromide and gives almost exclusively bromofumaric acid. The elimination of hydrogen fluoride from the two above-mentioned acids is faster by 1–2 orders of magnitude than the elimination of hydrogen fluoride from any fluorinated succinic acids. Kinetic data based on ¹H NMR measurements are presented and possible mechanisms and stereochemistry involved are discussed.     

A case of oligomerization on attempted chlorination of an α-hydroxy acetal with the triphenylphosphine tetrachloromethane reagent

Treatment of methyl 3,5-dideoxy-β-$\text{D}$-$\text{erythro}$-pentofuranoside $\text{8}$ with the Ph₃P-CCl₄ reagent gave none of the expected 2-chloro derivative but a mixture of l→2 linked oligosaccharides, $\text{9}$, $\text{10}$ with some higher homologues, terminated by αa 2-chloro-2,3,5-trideoxy-α-$\text{D}$-$\text{threo}$-pentofuranosyl unit at the non reducing end.