Diastereomeric Sulfoxides Research Articles

ChemInform Abstract: Functionally Substituted Vinyl Carbanions. Part 38. C‐Glucosides by Direct 1‐C‐Lithiation of 2‐Phenylsulfinyl‐Activated D‐Glucal.

AbstractLithiation of the diastereomeric sulfoxides (I) (of uncertain assignment) and subsequent treatment with either propionaldehyde (II) or the arabinose derivative (V) yields the epimers (III)/(IV) and (VI)/(VII).

ChemInform Abstract: Pummerer Rearrangements and Similar Reactions of Some Six‐Membered Cyclic Sulfoxides: Synthesis of 3‐Deoxy‐5‐thiopentopyranoses Branched at C‐3.

AbstractOxidation of the meso‐3,5‐diacetoxytetrahydrothiopyrans (I) with MCPBA produces mixtures of the diastereomeric sulfoxides (II) and (III).

Asymmetric oxidation of thioethers. Optical resolution of [1,1′-binaphthalene]-2,2′-dithiol

Almost optically pure (e.e. > 98%) [1,1′-binaphthalene]-2,2′-dithiol ( 2) is obtained by resolution of racemic 2 via the transformation of the sulfidryl functions into the corresponding thioethers 3 which are asymmetrically oxidized to diastereomeric chiral monosulfoxides 4 and then reconverted into 2. The diastereo and enantioselectivity is dependent on the structure of the thioether; i.e. the dimethylthioether 3a gives two diastereomeric sulfoxides 4a in ca. 1:1 ratio, each of them in > 98% e.e., while cyclic dithioethers 3b–d afford a single diastereomeric sulfoxide 4b–d in 46–78% e.e..

ChemInform Abstract: Double Stereoselection in the Sulfoxidation Reaction Catalyzed by Titanium Complexes of N‐Salicylidene‐L‐amino Acids.

AbstractOxidation of the optically active sulfide (I) with the oxotitanium complex of N‐salicylidene‐L‐leucine A) gives the diastereomeric sulfoxides (IIa) and (IIb) with 24% e.e.

ChemInform Abstract: Stereoisomeric Flavor Compounds. Part 16. Structure and Properties of Optically Pure 2‐Methyl‐4‐propyl‐1,3‐oxathiane 3‐Oxides.

AbstractFrom optically pure (2S,4R)‐oxathiane (I) the diastereomeric sulfoxides (II) and (III) are obtained.

ChemInform Abstract: Chiral Epoxides as Recoverable Auxiliaries in the Synthesis of Optically Active Sulfinyl Dienophiles.

AbstractThe chiral styrene oxide (I) is converted to the diastereomeric sulfoxides (IV).

ChemInform Abstract: (α‐(Phenylsulfinyl)‐α‐methylbenzyllithium‐tetramethylethylenediamin# e)2: Crystal Structure of an α‐Sulfinyl “Carbanion”.

AbstractThe title compound (II), formed as only one diastereomer from a ca. 1:1 mixture of the two diastereomeric sulfoxides (I) as shown in the scheme, is characterized by the first X‐ray structure analysis of a lithiated sulfoxide (space group C2/c, Z = 8).

Linear and Cyclic Enkephalin Pseudopeptides. Use of RP-HPLC to Separate and Identify Diastereomers Formed during Synthesis

Abstract During the course of synthesis of both a linear and a cyclic enkephal in pseudopeptide containing a ψ[CH2S] amide bond replacement, two isomeric products were produced in each case in virtually equimolar quantities. RP-HPLC was used to: 1) isolate and characterize both pairs of products; 2) confirm their sulfide content by partial oxidation to their ψ[CH2SO] equivalents, with two new pairs of diastereomeric sulfoxides formed in each case, and 3) confirm that the isomers were formed by epimerization of the C-terminal alpha carbon of the pseudopeptide, H-Tyr-D-Ala-Gly-Pheψ[CH2S]Leu-OH and its cyclic counterpart in an early synthetic step. Both the presence and the absolute configurations of the new epimeric center were further established by RP-HPLC. This involved acid catalyzed hydrolysis and comparison of the resulting HPLC-isolated pseudodipeptides with authentic species of Pheψ[CH2S]Leu and Pheψ[CH2S]D-Leu prepared by controlled stereochemical routes.

Stereoselectivity of chloroperoxidase-dependent halogenation.

The stereoselectivity of chloroperoxidase halogenation of four substrates has been examined. Chloroperoxidase catalyzes the bromination, but not chlorination, of racemic 2-exo-methylbicyclo[2.2.1]hept-5-ene-2-endo-carboxylic acid (to the delta-lactone) and racemic bicyclo-[3.2.0]hept-2-en-6-one (to the 2-exo-bromo-3-endo-hydroxy-bromohydrin). These products are obtained in near quantitative yield and are racemic. The circumstances of the bromination strongly suggest that halogenation does not occur at the active site but rather by chloroperoxidase-catalyzed formation of Br2 and its release into solution. The inability of chloroperoxidase to halogenate these two alkenes at its active site most probably derives from a steric exclusion from the active site. The stereoselectivity of two additional substrates that undergo active site chlorination was determined. Methionine is quantitatively converted to a 50:50 ratio of the two methionine sulfoxide diastereomers. 2-Methyl-4-propylcyclopentane-1,3-dione is quantitatively chlorinated to 2-chloro-2-methyl-4-propylcyclopentane-1,3-dione. On the basis of optical rotation and proton nuclear magnetic resonance, this product is present as a 40:60 ratio of the racemic diastereomers. It is concluded that active site chlorination by chloroperoxidase proceeds without appreciable stereoselectivity.

Preparation, Characterization and Reactivity of Diastereomeric Sulfoxides of 8,2′-S-Anhydroadenosine

Abstract The oxidation of 8,2′-S-anhydroadenosine (1a) has been investigated. The major product from the oxidation of 1a using 1-chlorobenzotriazole was the R-sulfoxide. The oxidation of 3′,5′-di-O-acetyl-8,2′-S-anhydroadenosine (1b) gave predominately the S-sulfoxide. These sulfoxides were found to be very succeptible to nucleophilic attack at C-8.

ANALOGS OF AMANIN

Ile3-amaninamide (3-R) and its diastereomeric sulfoxide (3-S) are obtained by oxidation of the bicyclic thioether peptide 2 by hydrogen peroxide in acetic acid. 2 was prepared by an intramolecular Savige-Fontana reaction of the linear octapeptide tert.-butylester 4 whose N-terminal Boc-Hpi residue on treatment with TFA loses the Boc group and reacts under thioether formation with the released cysteine-SH. The concomitantly deprotected carboxyl terminus is coupled intramolecularly with the free amino group of the secocompound 5 using the MA or DCCI method, thus forming the homodetic peptide ring. Compounds 3-R and 3-S agree very well with analog samples in chiroptical behavior. Thioether 2 and sulfoxide 3-R exert 50% inhibition of RNA polymerase II (or B) from Drosophila melanogaster in 10(-6) M solution whereas Ki of 3-S is about five times higher.

Synthesis of homolanthionine sulfone and homolanthionine sulfoxide

Homolanthionine sulfoxide and homolanthionine sulfone were obtained by oxidation of homocystine with hydroperoxide in acid solution. Homolanthionine sulfone was isolated and crystallized following ion exchange chromatography. Homolanthionine sulfoxide diastereomers were identified in the reaction mixture.