Intramolecular azide cycloaddition to a photochemically generated zwitterion

Photochemical rearrangements of 2,5-cyclohexadienones $\text{7a}$ and $\text{7b}$ to bridged triazenes $\text{11a}$ and $\text{11b}$$\text{via}$ zwitterions $\text{10a}$ and $\text{10b}$ are described.     

Palladium-catalyzed cyclization reactions : Unique synthesis of condensed thiazoles

The facile synthesis of 3-methylene-2,3-dihydro-5H-thiazolo-[3,2-c]pyrimidin-5-ones ($\text{9}$) has been performed by the catalytic action of a Pd(II) salt on 4-propargylthiopyrimidin-2(1H)-ones ($\text{6}$).Similar Pd(II)-catalyzed cyclization of 3-propargylthio-1,2,4-triazin-5(2H)-ones ($\text{10}$) gives 6-methylene-6,7-dihydro-4H-thiazolo[2,3-c](1,2,4]-triazin-4-ones ($\text{11}$) as a main product. 3-Methylene-2,3-dihydro-7H-thiazolo[3,2-b][1,2,4]triazin-7-ones ($\text{12}$), the regioisomers of $\text{11}$ are provided by a base-catalyzed cyclization of [ulbar 10].     

(10R̃, 11R̃)-(+)-squalene-10, 11-epoxide: Isolation from Laurencia okamurai and the asymmetric synthesis

From a red alga $\text{Laurencia okamurai}$ (10$\text{R}\text{?}$, 11$\text{R}\text{?}$)-(+)-squalene-10, 11-epoxide $\text{1}\text{?}$ was isolated and its asymmetric synthesis has been achieved starting from $\text{trans, trans}$-farnesol.     

Synthesis and reactions of substituted nitro-allylating reagents

Nitro-cyclohexenylation and α-phenyl-nitro-allylation of nucleophilic centres are achieved (see $\text{11}$-$\text{16}$) with the nitroallyl pivalates $\text{2}$ and $\text{5}$, and with the chloride $\text{3}$, which are in turn prepared from the diols $\text{9}$ and $\text{10}$, respectively.     

The invention of new radical chain reactions. part X: High yield radical addition reactions of αβ-unsaturated nitroolefins. An expedient construction of the 25-hydroxy-vitamin D3 side chain from bi

Radicals derived from thiohydroxamic esters $\text{3}$ readily add to nitroolefins $\text{5}$ (Z = NO₂) to give good yields of α-nitrosulphides. These adducts, where the structure permits, are easily oxidised to carboxylic acids $\text{8}$ by treatment with alkaline hydrogen peroxide. Reductive cleavage to the corresponding aldehydes or ketones $\text{9}$ is efficiently carried out by the action of TiCl₃. Addition of methyl magnesium iodide to the methyl ketone derived from 3α-acetoxy 11-oxo cholanic acid gives steroid $\text{10}$ possessing the 25-hydroxycholesterol side chain of the vitamin D₃ metabotites. Radical additions to 1-phenylthio-2-nitropropene $\text{11}$ have been briefly studied.     

The absolute configuration of berberastine and thalidastine

Optical resolution of (±)-tetrahydrojatrorrhizine using (-)-O,O-di-$\text{p}$-toluoyl-$\text{d}$-tartaric acid gave rise to (+)-tetrahydrojatrorrhizine ($\text{6}$ of high optical purity and of known absolute configuration. Oxidation of this enantiomer with lead tetraacetate, followed by acid hydrolysis, furnished alcohols $\text{10}$ and $\text{11}$ in a 2:1 ratio, whose relative stereochemistry was established from their nmr spectra. Iodine oxidation of the major alcohol $\text{10}$ led to protoberberinium salt $\text{14}$ which was found to be dextrorotatory. Since berberastine ($\text{1}$) and thalidastine ($\text{2}$) are also dextrorotatory, they must possess the same absolute configuration as $\text{14}$.     

Cyclic tautomers of tryptamines and tryptophans. V. Formation and reactions of cyclic tautomers of cyclo-L-tryptophanyl-L-proline

Two stereoisomeric cyclic tautomers ($\text{5}$ and $\text{6}$ of cyclo-L-tryptophanyl-L-proline whose stereochemistry was established by x-ray analysis, gave 5- and 6-hydroxytryptophanyl derivatives ($\text{10}$), $\text{11}$, and $\text{19}$) on the hydroxylation with lead tetraacetate in trifluoroacetic acid.     

Reaction of acetoxyazetidinones with trimethylsilylacetyl thiolesters: preparation of azetidinone-thiolester precursors to carbapenems

Reaction of acetoxyazetidinones, $\text{1}$ and $\text{2}$, with trimethylsilyl- acetyl thiolesters $\text{10}$ afforded azetidinone-thiolesters, $\text{11}$ and $\text{12}$, which are useful intermediates in the carbapenem synthesis.     

The synthesis and x-ray crystal structure of a tetracyclo[4.2.1.1.2,503,7]decane derivative. A rigid,twist boat-containing ring system.

Attempted intramolecular pinacolization of cage diketone $\text{4}$ unexpectedly gave ketol $\text{5}$ instead. Compound $\text{5}$ was shown to possess the rare tetracyclo[4.2.1.1.^2,50^3,7]decane ring system by means of an X-ray crystal structure of hydroxy-mesylate $\text{10}$ derived from $\text{5}$ by sodium borohydride reduction followed by mesylation. A possible mechanism for the transformation of $\text{4}$ into $\text{5}$ is presented, and certain noteworthy features of the crystal structure of $\text{10}$ are discussed. The base-catalysed fragmentation of $\text{10}$ to give enone $\text{11}$ is also described.     

Crahamimycin A1 synthesis and determination of configuration and chirality

The two hydroxyacid derivatives $\text{10}$ and $\text{11}$, obtained from (S)-β-hydroxybutanoate and (S)-lactate, respectively, are joined to give the acetylenic ester $\text{12}$. Cyclization and functional group manipulations lead to (S,S)-(+)-grahamimycin A₁, the enantiomer of the natural product.     

Etude des reactions des diazoderives avec les cycloimmonium ylures-I : Action des sels de diazonium sur quelques pyridinium - ylures

The synthesis of cycloimmonium salts of the type $\text{7}$, $\text{8}$ and the corresponding cycloimmonium ylides $\text{9}$, $\text{10}$ are reported. In the reaction with diazonium salts $\text{11}$, $\text{12}$ the pyridinium monosubstituted carbanion ylides $\text{9}$, $\text{10}$ give the pyridinium disubstituted carbanion ylides $\text{17}$ – $\text{20}$. These are new types of isolable stable ylides. The synthesis involves the formation “in situ” of ylides $\text{9}$, $\text{10}$ which are bonded by their nucleophile ylide carbon atom to the nitrogen atom in diazonium salts. The intermediat formation of cycloimmonium salts $\text{13}$ – $\text{16}$ must be accepted. The structures of all compounds presented in this paper have been established by using elementary analysis, IR and ¹H-RMN spectra.     

Ciral synthons for the multistriatins

The readily-obtained carbohydrate α-enones $\text{2}$, $\text{5}$ and $\text{8}$ are converted into the four diastereomeric 2,4-di-C-methyl glycopyranosides $\text{4}$$\text{7}$,$\text{10}$,$\text{11}$, which are chiral synthons for the four multistriatins $\text{1a}$-$\text{1d}$.     

Syntheses of trifluoromethylated diene derivatives through the claisen rearrangement of trifluoromethylated propargylic and allylic alcohols

3-Trifluoromethyl-2Z, 4E-dienoate ($\text{14}$) and the dienamide ($\text{10}$,$\text{11}$) were prepared through the Claisen rearrangement of trifluoromethylated propargylic and allylic alcohols.     

Investigations on diazo compounds and azides- LXII.: Synthesis and reactions of a-diazo phosphonates with a conjugated 1,3-diene unit

α-Diazo phosphonates with a conjugated 1,3-diene unit are synthesised by the Bamford-Stevens reaction ($\text{2}$ →$\text{4}$→$\text{3}$). They undergo [4+2]-cycloadditions with the dienophile $\text{5}$ to form the tetrahydrotriazolopyridazines $\text{8}$, which possess an unchanged diazo group. In contrast, dimethyl acetylenedicarboxylate ($\text{9}$) reacts exclusively with the diazo dipole of $\text{3}$ to yield the 3H-pyrazoles $\text{10}$, which rearrange to $\text{11}$ by sigmatropic PO-shifts and hydrolyse to form $\text{13}$. The diazo compound $\text{3b}$ isomerises to the pyrazole $\text{16}$ when heated in benzene.     

Synthesis and conformational behaviour of 1,9,17-triaza[2.2.2]metacyclophane-2, 10, 18-trione derivatives

The 1,9,17-triaza[2.2.2]metacyclophane-2, 10, 18-trione derivatives ($\text{1}$) – ($\text{3}$) have been synthesised. X-Ray crystallography shows that the 1,9,17-trimethyl derivative ($\text{3}$) adopts a Crown conformation ($\text{11}$) in the solid state. Dynamic n.m.r. spectroscopy indicates that both the 1,9-dimethyl-17-benzyl- ($\text{2}$) and 1,9,17-trimethyl- ($\text{3}$) derivatives exist as interconverting mixtures of Crown ($\text{11}$) and Saddle ($\text{12}$) conformations with the former predominating at equilibrium in solution.     

Syntheses of enantiomeric dihydropyrans through stereocontrolled intramolecular cycloaddition

Reaction of the cyclic 1, 3-dicarboxylic acid derivatives ($\text{1}$), ($\text{2}$) and ($\text{3}$) with (R)- or (S)-citronellal ($\text{4}$/$\text{5}$) gives the enantiomeric tricyclic dihydropyrans ($\text{10}$), ($\text{11}$), ($\text{12}$) and ($\text{13}$), probably via a 100% stereocontrolled intramolecular cycloaddition.     

New terpenoid aldehydes from Kigelia pinnata: crystal structure of pinnatal

From the root bark of Kigelia pinnata (Bignoniaceae) two aldehydes, norviburtinal(6-formylcyclo-penta[c]pyran) and pinnatal, 11-formyl-2, 3, 3a, 5, 10, 10a, 11, 11a-octahydro-8-hydroxy-3, 11-dimethyl-3, 10a-epoxy-1$\text{H}\text{-}$-cyclopent[b]anthracene-5, 10-dione, have been isolated. The structures were determined by spectroscopic methods, and X-ray crystallographic analysis of pinnatal.     

[O9,24] [2.1.2.1] metacyclophane-9-ene,a “twin cyclophane”, and its dehydrogenation products - synthesis structure determination and 1H-NMR-spectroscopy

The synthesis of [O⁹,24] [2.1.2.1]metacyclophane-9-ene and of its dehydrogenation products^the new pyrenocyclophanes $\text{8}$, $\text{10}$, $\text{11}$, and $\text{12}$, is described; their structures are discussed in connection with their ¹H-NMR-spectra.     

An efficient conversion of berberine into a rhoeadine via an indenobenzazepine

Treatment of ketoaziridine $\text{4}$ with aqueous formaldehyde gives the unusual bridged indenobenzazepine derivative $\text{6}$ whose reduction uith sodium cyanoborohydride produces trans ketol $\text{8}$. In the presence of hydrochloric acid, $\text{8}$ undergoes irreversible conversion to the more stable cis ketol $\text{10}$. Periodate oxidation of $\text{8}$ supplies γ-laotone $\text{11}$. NaBH₄ reduction of $\text{11}$ followed by acid treatment affords δ-lactone $\text{12}$ which upon reduction and O-methylation furnishes cis rhoeadine analog $\text{14}$.