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.     

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]     

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.     

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.     

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.     

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.     

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.     

Plasma chemical synthesis. II. Effect of wall surface on the synthesis of ammonia

The plasma synthesis of ammonia was stuided at pressures of 1–5 torr and flow rates of up to 200 torr cm³ min^–1 using Pyrex and silver surfaces cooled to 77 K. The N conversion to ammonia was about 13% in experiments in which the afterglow was trapped on the Pyrex surface. By quenching the plasma rather than the afterglow, the percent N conversion could be doubled using the Pyrex surface and quadrupled using the silver surface. Increasing the hydrogen pressure and/or hydrogen discharge cleaning decreased the percent N conversion; nitrogen discharge conditioning had no significant effect. With increasing nitrogen flow rate the percent N conversion decreased linearly in the quenched plasma reaction on the silver surface, suggesting nitriding and reduction by hydrogen to form ammonia. The exponential decrease of the percent N conversion in the quenched afterglow reaction on the Pyrex surface is explained by the formation and/or dissociation of adsorbed N₂ determining the ammonia yield at 77 K.     

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.     

Phase managed organic synthesis 2. A new polymer assisted synthesis of acid anhydrides.

A solid-phase copolymer of 4-vinylpyridine is shown to be a highly effective reagent/ catalyst for the synthesis of acid anhydrides from mixtures containing equimolar quantities of carboxylic acids and acid chlorides. The process may be carried out in batch or column mode.     

Thallium in organic synthesis. 68. A convenient synthesis of 2-phenylindoles from anilides

Thallation of anilides with TTFA in a mixture of TFA and ether gives ortho-thallated derivatives, which yield 2-acetamido-tolanes upon reaction with copper(I) phenylacetylide in acetonitrile. Treatment of the latter compounds with palladium(II) chloride results in ring closure to give 1-acyl-2-phenylindoles, from which 2-phenyl-indoles are obtained by alkaline hydrolysis.     

Polyamide synthesis by ester aminolysis. I. A new route for nylon-6,6 synthesis

A new route for nylon-6,6 synthesis has been studied. The process is grounded on the synthesis of an α-amino ω-ester monoamide precursor (AME-6,6) easily available in reacting in the bulk hexamethylene diamine and dimethyl adipate at a low temperature (T ≅ 50°C) preferably in the presence of a phenol derivative. In such conditions AME-6,6 precipitates with a very good yield (90–95%). One of the greatest advantages of AME-6,6 is to keep the stoichiometric balance for further polyamidation; that is not the case in other processes. Moreover AME-6,6 is very stable, e.g., even stored at room temperature under air during 50 days. Polyamides-6,6 have been obtained from AME-6,6 (used freshly prepared or after storage) in glass laboratory reactors by direct heating under vacuum (T = 270°C) with number-average molecular weights of roughly 20,000. © 1996 John Wiley & Sons, Inc.     

Exploring the mechanism for the synthesis of silsesquioxanes. 4. The synthesis of T8

In an attempt to explore the mechanism for the synthesis of silsesquioxanes (POSS), the entire reaction processes from HSi(OH)3 to T8, one of the most common and stable POSS was investigated with electronic structure theory calculations, including electron correlation effects. In addition, the effect of some controlling factors, which play important roles in the reaction mechanism, is discussed.