Fluorinated chromenes 1: 2,2,2-trifluoroethoxy precocene analogs and their corresponding 3,4-epoxides

Preparation of potential insect antijuvenile hormone agents 2,2-dimethyl-7-(2,2,2-trifluoroethoxy)-2H-chromene ($\text{3a}$), 6-methoxy-2,2-dimethyl-7-(2,2,2-trifluoroethoxy)-2$\text{H}$-chromene ($\text{3b}$) and 7-methoxy-2,2-dimethyl-6--(2,2,2-trifluoroethoxy)-2$\text{H}$-chromene ($\text{3c}$) and the corresponding 3,4-epoxides $\text{5a}$ and $\text{5b}$ is reported.     

Sigmatropic 1.5-hydrogen shift and concomitant cyclopropane bond cleavage on thermolysis of trans-1-isopropenyl-4-methylene spiro[2.x]alkanes into 1-methylene-(3′-methylbut-2′-enyl)-cycloalk-2-enes

Thermolysis of several trans-1-isopropenyl-4-methylene-spiro[2.x]- alkanes (x = 4,5) in xylene solution at 130° causes quantitative rearrangement to 1-methylene-2-(3′-methylbut-2′-enyl)cycloalkanes ($\text{3}$ – $\text{4}$).     

Synthesis of 2-isopropylfuro(2,3-b)quinolines-a new synthesis of (±)-lunacrine, (±)-lunasine and (±)-demethoxylunacrine

A new and convenient synthesis of 2-isopropylfuro-(2,3-b)quinolines ($\text{4}$) from 3-(3-methylbut-1-enyl)-2-quinolones ($\text{2}$) is described. A neat synthesis of the alkaloids (±)-lunacrine ($\text{1a}$), (±)-lunasine ($\text{12a}$) and (±)-demethoxylunacrine ($\text{1b}$) is also reported.     

Naturally occurring 5-methyoxy-3(2H)-furanones. Re-assignment of structures to the aspertetronin group of natural products

Synthetic and spectroscopic investigations establish that the aspertetronin (also known as gregatin and graminin) group of natural products isolated from $\text{Aspergillus}$ and $\text{Cephalosporium sp}$., has the 5-methoxy-3(2H)-furanone structure (4) rather than the previously assigned O-methyl tetronic acid structure (3).     

6-alkyl- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones in the transformations of pyrimidines. Regiospecific 1-N-acylation of pyrimidines.

Transformation of 6- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones (1a and 1b) into 1-$\text{N}$-acylated-pyrimidine derivatives 3($\text{a}$-$\text{f}$) under Friedel-Craft like conditions is presented. In different acylation conditions 4-O-acylated-pyrimidines (5a and 5b) are also obtained. Compounds (3c) and (3f) can be directly converted into 1-$\text{N}$-acyl-protected-isouridine analogues (8a and 8b).     

The naphthalene route to anthracyclinones

A regiospecific total synthesis of 6,11-dihydroxy-4-methoxy-7,8,9,10-tetrahydro-5,12-naphthacenedione-9-carboxylic acid methyl ester ($\text{3}$) was synthesized from the key intermediate ($\text{2}$).     

A convenient synthesis of substituted γ-pyrones

An efficient and general synthetic method for various 2-mono- and 2,6-disubstituted γ-pyrones has been developed. This utilizes the $\text{C}$-acylation (70–85%) of β-methoxy-α,β-enone lithium enolates $\text{4}$ by acid chlorides $\text{3}$ followed by the acid-catalyzed cyclization (>80%) of the resulting enols $\text{5}$ to γ-pyrones $\text{6}$.     

v-Triazolines. part XXI. Spiro[bicyclo[2.2.1]hept-2-ene[54']1',2'.s'-triazole]derivatives from cyclopentadiene and 5-amino-4-methylene-v-triazolines

1R^*, 4R^*, 5S^*, 5'S^*-5'-Amino-1'-(4-nitrophenyl)-4',5'-dihydrospiro[bicyclo [2.2. 1]hept-2-ene[5.4]-1',2',3'-triazoles]$\text{2}$ have been obtained both by ?4 +2]-cycloaddition of cyclopentadiene to amino-methylene-1-(4-nitrophenyl)-4,5-dihydro-v-triazoles $\text{1}$ and by [3+2]-cycloaddition of 4-nitrophenylazide to 5-aminomethylene-2-norborenes $\text{4}$. The configuration has been fully established by X-ray crystallographic analysis. The course of the cycloaddition and the thermal behaviour of $\text{2}$ are discussed.     

Bridgehead nitrogen heterocycles from 2,4,6-triphenyl- pyrylium cation and thiosemicarbazide or thiocarbohydrazide

2,4,6-Triphenylpyrylium with thiosemicarbazide and thiocarbohydrazide, gives 2-pyrazolines $\text{3a}$ and $\text{3b}$ which undergo cyclization yielding pyrazolo(1,5-c]pyrimidine 5 and pyrazolo [2,3-d]-1,2,4-triazepine $\text{7}$ derivatives, respectively. Reaction of $\text{7}$ with phenacyl bromides gave 1,3-thiazolo[3,2-b]pyrazolo [2,3-d]-1,2,4-triazepin-4-iums $\text{10}$. Compound $\text{3a}$ on treatment with phenacyl bromides gave 1-(4'-aryl-thiazol-2'-yl)-2-pyrazoline derivatives $\text{6}$. Compound $\text{3b}$ reacts with acyl chlorides to give pyrazolo[1,5-c]pyrimidine derivatives $\text{14}$, and with aromatic aldehydes giving the 2-(Δ^2'1 pyrazolin-1-yl)-5-aryl-1,3,4-Δ²-thiadiazolines $\text{12}$ which were easily converted to the corresponding 2-(Δ²-pyrazolin-1-yl)-5-aryl-1,3,4-thiadiazoles $\text{13}$.     

On the mode of incorporation of leucine samples labelled at positions 5 and 2 with 3H and 14C into the isoprenylated tryptophan derivative echinuline from aspergillusamstelodami

Feeding experiments with (4$\text{S}$) [5-³H;5-¹⁴C]$\text{L}$-leucine ($\text{1a}$) and with the (4$\text{S}$) [5-³H;2-¹⁴C]-isomer ($\text{1b}$) show that incorporation into the isoprenylated tryptophan derivative echinuline ($\text{3}$), produced by $\text{Aspergillus}$$\text{amstelodami}$, involves, to a large extent, loss of the fragment enbodying the carbon atom at position 2 of the fed amino acid.     

A one-step synthesis of γ-pyrones

The potassium enolate of 4-methoxy-3-buten-2-one reacts with acid chlorides anhydrides and acylimidazoles by C-acylation and $\text{in situ}$ cyclization to afford 2-substituted γ-pyrones directly.     

Zeyloxanthonone,a new tetrahydroxanthone from calophyllum zeylanicum (guttiferae)

Zeyloxantonone, a triprenylated tetrahydroxanthone isolated from $\text{C. zeylanicum}$ has been show to be 6,8-dihydroxy-1,1,7-tri(3-methylbut-2-enyl)-2-oxo-1,2,3,4-tetrahydroxanthen-9-one (I) by chemical and specroscopic methods.     

A Wittig reaction on mucochloric and mucobromic acids. Preparation of ethyl (2E, 4Z -4,5-dihalo-2,4-pentadienoates and alkyl 2E -5-bromo-2-penten-4-ynoates

Reaction of mucochloric and mucobromic acid with (ethoxycarbonylmethylene) triphenyl-phosphorane affords the ethyl ester of (2$\text{E}$, 4$\text{Z}$ -4,5-dichloro- and (2$\text{E}$, 4$\text{Z}$) -4, 5-dibromo-2,4-pentadienoic acid respectively; in the latter case ethyl (2$\text{E}$ -5-bromo-2-penten-4-ynoate is formed concomittantly.     

Reaction of 2-methoxy-1,3-dioxane with grignard reagents: reagent-substrate complexation and stereoelectronic control.

The stereoelectronically controlled reaction of 2-methoxy-1,3-dioxane ($\text{1}$) with Grignard reagents does not follow the course suggested by the behavior of anancomeric models for the conformational isomers of $\text{1}$. Treatment of $\text{1}$ with RMgX leads to the predominant formation of acid labile 3-(1′-methoxyalkoxy)-1-propanols, derived from endocyclic cleavage of the ring CO bond, and only minor amounts of the expected 2-R-1,3-dioxanes.     

The octant rule. XIV. synthesis and circular dichroism of α-exo and endo-deuteriobicyclo[3.2.1]octan-3-one and 6,6-dimethybicyclo[3.1.1]heptan-3-one

(1R,5S)-2S-Deuteriobicyclo[3.2.1]octan-3-one ($\text{1}$) and (1R,5S)-2R-Deuteriobicyclo[3.2.1]octan-3-one ($\text{2}$), prepared by diazomethane ring enlargement of (1S,4R)-2(exo)-deuteriobicyclo-[2.2.1] heptan-2-one and (1S,4R)-2(endo)-deuteriobicyclo[2.2.1]heptan-2-one respectively, both gave (?) n-π^* circular dichroism (CD) Cotton effects, Δε^max₂₉₄ = ?0.05 and Δε^max₂₉₄=?0.1, respectively, in hydrocarbon solvent. (1S,5R)-2S-Deuterio-6,6-diaethylbicyclo[3.1.1] heptan-3-one ($\text{3}$) and (1S,5R)-2R-deuterio-6,6-dimethylbicyclo[3.1.1] heptan-3-one ($\text{4}$), prepared from (-) myrtenal, both exhibited extraordinary vibrational fine structure for the n-π^* CD transitions observed in hydrocarbon solvent and oppositely?signed CEs, Δε^max₂₈₂=?0.01 and Δε^max₂₇₉=+0.01 respectively in CF₃CH₂OH solvent.     

Reaction of acylaminocyanoesters with 2,4-bis (4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide leading to substituted aminothiazoles. Crysta

2-Acylamino-2-cyanoacetic acid ethyl esters $\text{2a-c}$ react with 2,4-bis (4-methoxyphenyl)-1, 3, 2, 4-dithiadiphosphetane 2,4-disulfide $\text{1}$ in refluxing benzene with formation of 2-alkyl(aryl)-5-aminothiazole-4-carboxylic acid ethyl esters $\text{3a-c}$. Structure $\text{3}$ was established by spectroscopic means and an X ray crystallographic investigation of $\text{3a}$. X-Ray analysis revealed that the thiazole ring, exocyclic nitrogen and carbonyl group forming a hydrogen-bonded cycle are nearly coplanar. A resonance interaction is manifested by distinctly shortened /1.447 (3)/ C_(carbonyl)-C_(thiazole) distance.     

Isolation ofΔ9(11)-sterols from the sea cucumber psolusfabricii. Implications for holothurin biosynthesis

- 14α-Methyl-5α-cholest-9(11)-en-3β-ol ($\text{2}$) and 4α,14α-dimethyl-5α-cholest-9(11)-en-3β-ol ($\text{3}$) have been isolated from the sea cucumber $\text{Psolus}$$\text{fabricii}$ and characterised by ¹H NMR, ¹³C NMR and mass spectrometry. Lanost-9(11)-en-3β-ol ($\text{4}$) has also been tentatively identified. The relevance of this series of Δ⁹⁽¹¹⁾-sterols to holothurin biosynthesis is briefly discussed.     

Synthesis of 4′-amino-4′-deoxy analog of pantothenic acid

The synthesis of $\text{D}$- and $\text{L}$-N-(4-amino-3, 3-dimethyl-2-hydroxybutyryl)- β-alanine ($\text{7}$) is described. Compound $\text{7}$ is an analog of pantothenic acid in which the 4′-hyroxy group is replaced by amino group. The synthetic sequence leading to $\text{7}$ involved the synthesis $\text{D}$L-4-amino-3,3-dimethyl-2-hydroxybutyric acid and its resolution. Coupling of N-benzyloxycarbonyl N-hydroxysuccinimide ester ($\text{5}$) with β-alanine and followed by removal of the protecting group gave $\text{7}$.     

Cycloaddition of singlet oxygen and 4-methyl-1,2,4-triazoline-3,5-dione (MTAD) to methoxycyclooctatetraene (MCOT)

The endoperoxides $\text{6}$ and $\text{7}$, respectively 9-methoxy- and 1-methoxy-7,8-dioxabicyclo[4.2.2]deca-2,4,7-trienes, and the urazoles $\text{8}$ and $\text{9}$, respectively 9-methoxy- and 2-methoxy-7,8-diazantricyclo[4.2.2]deca-2,4,9-trien-$\text{N}$-methyl-7,8-dicarboximide, were obtained in the cycloaddition of singlet oxygen and $\text{4}$-methyl-1,2,4-triazoline-3,5-dione (MTAD) to methoxycyclooctatetraene (MCOT).