Benzothiazines in synthesis. Formal synthesis of erogorgiaene

A benzothiazine, readily available in enantiomerically pure form via a completely selective, intramolecular addition of a sulfoximine-stabilized carbanion to an α,β-unsaturated ester, could be converted to a precursor to erogorgiaene in good overall yield.     

Free radical reactions in synthesis. Total synthesis of isoamijiol.

The dolastane carbon framework present in isoamijiol(1) is elaborated from the enamine(5) using seven carbon-carbon bond forming reactions, four of which involve free radical intermediates.     

Enynones in organic synthesis. III. A novel synthesis of phenols

Enynones are converted to phenols by an acid catalyzed process which can be controlled to give either of two regioisomeric series of products.     

Total synthesis of (+)-pederin. 1. Stereocontrolled synthesis of (+)-benzoylpedamide

(+)-Benzoylpedamide (5), a right half of (+)-pederin (1), was synthesized stereoselectively based on the newly developed method for the synthesis of 1,3-$\text{syn}$-and 1,3-$\text{anti}$-polyols.     

Benzothiazines in synthesis. Toward the synthesis of pseudopteroxazole

[reaction: see text] The tricyclic benzothiazine 15 was prepared in a straightforward fashion via a completely stereoselective intramolecular Friedel-Crafts alkylation. This compound represents a potential precursor to the antitubercular agent, pseudopteroxazole. Its synthesis proceeded via a completely selective, intramolecular addition of a sulfoximine-stabilized carbanion to an alpha,beta-unsaturated ester, followed by functional group manipulations.     

Benzothiazines in synthesis. A total synthesis of pseudopteroxazole

An enantioselective total synthesis of the naturally occurring antitubercular agent pseudopteroxazole is described. The synthesis is organized around the use of a stereoselective, intramolecular addition of a sulfoximine carbanion to an alpha,beta-unsaturated ester to form an enantiomerically pure benzothiazine. Other important processes include a completely stereoselective intramolecular Friedel-Crafts alkylation and a stereoselective and regioselective hydrogenation. [structure: see text]     

Amidoalkylation in organic synthesis.1. Total synthesis of isoretronecanol and trachelanthamidine

The title compounds are prepared in five steps from N-2-bromo ethyl succinimide.     

Thallium in organic synthesis. 63. A convenient synthesis of aromatic nitriles

Aromatic nitriles are readily formed by heating arylthallium bis(trifluoroacetates) with CuCN in acetonitrile.     

Total synthesis of (+)-pederin. 2. Stereocontrolled synthesis of (+)-benzoylselenopederic acid and total synthesis of (+)-pederin

(+)-Benzoylselenopederic acid (1), a left half of (+)-pederin (3), was synthesized stereoselectively based on the Zn(BH₄)₂ reduction and total synthesis of (+)-pederin (3) was accomplished from 1 and the previously synthesized 2.     

Improved synthesis of o-phosphohomoserine.

O-Phosphohomoserine (PHS) was prepared in an overall yield of 49% by treatment of N-benzyloxycarbonyl-homoserine p-nitrobenzyl ester with diphenylphosphoryl chloride in pyridine, followed by catalytic hydrogenolysis. Both L - and D , L -phosphohomoserine were found to be 100% hydrolyzed by alcaline phosphatase from E. coli.     

Benzene-free synthesis of hydroquinone.

All current routes for the synthesis of hydroquinone utilize benzene as the starting material. An alternate route to hydroquinone has now been elaborated from glucose. While benzene is a volatile carcinogen derived from nonrenewable fossil fuel feedstocks, glucose is nonvolatile, nontoxic, and derived from renewable plant polysacharrides. Glucose is first converted into quinic acid using microbial catalysis. Quinic acid is then chemically converted into hydroquinone. Under fermentor-controlled conditions, Escherichia coli QP1.1/pKD12.138 synthesizes 49 g/L of quinic acid from glucose in 20% (mol/mol) yield. Oxidative decarboxylation of quinic acid in clarified, decolorized, ammonium ion-free fermentation broth with NaOCl and subsequent dehydration of the intermediate 3(R),5(R)-trihydroxycyclohexanone afforded purified hydroquinone in 87% yield. Halide-free, oxidative decarboxylation of quinic acid in fermentation broth with stoichiometric quantities of (NH(4))(2)Ce(SO(4))(3) and V(2)O(5) afforded hydroquinone in 91% and 85% yield, respectively. Conditions suitable for oxidative decarboxylation of quinic acid with catalytic amounts of metal oxidant were also identified. Ag(3)PO(4) at 2 mol % relative to quinic acid in fermentation broth catalyzed the formation of hydroquinone in 74% yield with K(2)S(2)O(8) serving as the cooxidant. Beyond establishing a fundamentally new route to an important chemical building block, oxidation of microbe-synthesized quinic acid provides an example of how the toxicity of aromatics toward microbes can be circumvented by interfacing chemical catalysis with biocatalysis.     

Palladium-catalyzed synthesis of allenes.

Substituted allenes are selectively obtained in good yields from the reaction of Grignard reagents with propargylic or allenic halides in the presence of catalytic amounts of palladium chloride, triphenylphosphine and diisobutyl aluminum hydride, in tetrahydrofuran at room temperature.     

Aminohaloborane in organic synthesis. VI. A simple enantioselective aldol synthesis

A simple asymmetric aldol condensation of acetophenone and benzaldehydes was performed via chiral vinylaminodichloroborane. The enatioselectivity was compared with that by a similar method using magnesium and lithium.     

Enynones in organic synthesis. II. An electron transfer mediated synthesis of methylenecyclopentenones

The electrocyclizaton of enynones to methylenecyclopentenones is markedly accelerated by phenols and catechols having a low oxidation potential.