Chemical synthesis of the 5-́half molecule of E.coli tRNA2GLY

A tritriacontanucleotide which has the sequence of the 5$\text{-}\text{?}$half molecule of E.coli glycine tRNA₂, was synthesized by the phosphotriester method involving p-anisidate protection for the 3$\text{-}\text{?}$phosphate ends. Di- and trinucleotide units were prepared from 5$\text{-}\text{?}$dimethoxytrityl-2$\text{-}\text{?}$O-tetrahydrofuranyl-3?-O-(o-chlorophenyl)phosphoryl derivatives of uridine, N-benzoylcytidine, N-benzolyadenosine and N-iso-butyrylguanosine by condensation with 3$\text{,}\text{?}$5$\text{-}\text{?}$unprotected nucleosides followed by phosphorylation to give 3$\text{-}\text{?}$phosphodiester blocks. The 3$\text{-}\text{?}$terminal dimers and trimers were synthesized by using 3$\text{-}\text{?}$(o- chlorophenyl)phosphoro-p-anisidates instead of 3?,5?-unprotected nucleosides. The 3?-phosphodiesters of oligonucleotides with a chain length of larger than 5 were obtained by removal of the 3?-phosphoro-p-anisidate with isoamyl nitrite. The 5$\text{-}\text{?}$dimethoxytrityl group was removed by treatment with zinc bromide under anhydrous conditions. Fragments were designed to use common dimer blocks and to reduce the step for 5$\text{-}\text{?}$deblocking of larger fragments. Finally a 3$\text{-}\text{?}$phosphodiester block with a chain length of 20 was condensed with a 5$\text{-}\text{?}$OH component (tridecanucleotide). The fully protected 33 mer was deblocked and purified by chromatography. The structural integrity of the product was confirmed by mobility shift analysis and complete digestion with RNase T2.     

A short and efficient synthesis of 4-hydroxy-5-(1-hydroxyalkyl)-γ-butyrolactones

The cycloaddition of α,β-epoxyaldehydes or ketones ($\text{2}$) with the ketene acetal MeHC=C(OMe)₂ ($\text{1}$) gives epoxyoxetanes ($\text{3}$) in high yields. Without isolation they can be transformed into 4-hydroxy-5-(1-hydroxyalkyl)-γ-butyrolactones ($\text{6}$) via the epoxy esters $\text{4}$ and trihydroxy esters ($\text{5}$). The lactones $\text{6}$ appear to be valuable precursors for the synthesis of 5-(1-hydroxyalkyl)-3-methyl-2-5H-furanones ($\text{7}$) and 3-methyl-5-ylidene-2-5H-furanones ($\text{8}$)     

Efficient asymmetric synthesis of α-amino acids through hydrogenation of α,β-dehydroamino acid residue in cyclic dipeptides

A series of cyclo (Δaminoacyl-L-Ala) ($\text{4}$) (Δ=α,β-dehydro) were prepared from cyclo(Gly-L-Ala) and corresponding aldehyde, and hydrogenated with Pd black in MeOH. Chiral inductions producing cyclo (L-aminoacyl-L-Ala) ($\text{5}$) from $\text{4}$ were 96–99% in the case of L-Aba (2-aminobutanoic acid), L-Val, L-Leu, and L-App (2-amino-5-phenylpentanoic acid) as an L-aminoacyl moiety in $\text{5}$. Pure L-Leu, L-Aba, and L-App were synthesized in preparative scale from corresponding $\text{4}$ through asymmetric hydrogenation and acid-hydrolysis.     

Structures of simarinolide and guanepolide (x-ray analysis), new quassinoids from Simaba cf orinocensis

Simarinolide $\text{4a}$ and Guanepolide $\text{5a}$ are new quassinoids with a C₂₅ basic skeleton isolated from a member of the French Guyanan Simaroubaceae, Simaba cf orinocensis H.B.K. The structure $\text{4a}$ was established by spectral means and that of $\text{5a}$ by X-ray diffraction analysis. The previously known simarolide $\text{1}$ was also isolated.     

3-methylthio-1,2-dithiolylium salts : Reaction with 4-hydroxy-6-methyl-2H-pyran-2-one and 4-hydroxycoumarin

The reaction of 4- and 5-aryl-3-methylthio-1,2-dithiolylium iodides with 4-hydroxy-6-methyl-2$\text{H}$-pyran-2-one and 4-hydroxycoumarin has been studied. 4-Substituted salts yielded 3-aryl-7-methyl-2-thioxo-2$\text{H}$,5$\text{H}$-pyrano [3,2-c]pyran-5-ones and 3-aryl-2-thioxo-2H,5H-pyrano[3,2-c]benzo[e]pyran-5-ones, respectively, whereas 5-substituted salts gave rise to 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-6-methyl-2$\text{H}$-pyran-2,4-diones and 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-2$\text{H}$-benzo [b]-pyran-2,4-diones.     

The chemistry of phenalenium systems XXXIII. The Dibenzo[de;thi]naphthacenyl dication and the dianon

The dibenzo[de;hi]naphthacenyl dication ($\text{4}$) and dianion ($\text{5}$) have been generated from a mixture of the corresponding precursor hydrocarbons. The pmr spectra of $\text{4}$ and $\text{5}$ indicated that the positive and the negative charges were found to be fully delocalized over the molecules, respectively, consistent with the C_2v-symmetry structures. The pmr chemical shifts of $\text{4}$ correlate well with the Hückel charge densities.     

Synthesis of a fluorinated analog of the sex pheromone of the processionary moth thaumetopoea. pityocampa(denis and schiff.)

The synthesis of ($\text{E}$)-13-fluorohexadec-13-en-11-ynyl acetate $\text{1}$, a fluorinated analog of the sex pheromone of the processionary moth Thaumetopoea pityocampa is described. The synthetic scheme involves epoxidation of the double bond, regioselective opening of the oxirane ring with Olah's reagent, tosylation of the resulting fluorohydrin and dehydrotosylation. Structural features of the intermediate diastereomeric fluorohydrins $\text{4a}$ and $\text{4b}$ and tosylates $\text{5a}$ and $\text{5b}$ are also discussed on the basis of their ¹H and ¹⁹F NMR spectra.     

Chemistry of 4-membered cyclic nitrones (2, 3-dihydroazete 1-oxides); a novel one-step synthesis of N-acetoxy β-latams

2,3-dihydroazete 1-oxide $\text{1}$ reacts at room temperature with base, acid and lead tetraacetate to give the 5-hydroxyisoxazolidines $\text{4a}$ and $\text{4b}$, the 6H-1,2-oxazin-6-one $\text{7}$ and the N-acetoxy β-lactam $\text{8}$, respectively; the reaction with lead tetraacetate represents a simple one-step conversion of a 4-membered cyclic nitrone into a β-lactam.     

Total synthesis of (±)-cannabisativine

Total synthesis of the Cannabis alkaloid cannabisativine ($\text{1}$) was stereoselectively achieved for the first time in a racemic form starting from a dihydropyridine derivative ($\text{2}$) by way of $\text{3}$, $\text{4}$, and $\text{5}$.     

Synthesis and molecular structure of niobocene(tricarbonyl)(π-cyclopentadienyl)molybdenum with metalmetal bond and unusual coordination of carbonyl groups

(C₅H₅)₂NbBH₄ reacts with C₅H₅M(CO)₃Me in toluene solution in the presence of Et₃N to give binuclear complexes (C₅H₅)₂NbM(CO)₃C₅H₅ where M is Mo or W (IV and V, respectively). The structure of IV has been studied by X-ray diffraction (the crystals are orthorhombic, a 12.748(5), b 16.745(6), c 14.314 $\text{A/ac>}\text{?}$;; Z = 8, space group of Pbca, automatic difractometer Syntex P2_I, λ(Mo-K_α, 1382 reflections, R = 0.056, R_w = 0.058). Molecule IV contains a wedge-like sandwich (π-C₅H₅)₂Nb (NbC 2.37–2.48, CC (av) 1.42 $\text{A/ac>}\text{?}$;, angle between ring planes 49°) linked with the (π-C₅H₅)Mo(CO) fragment by a direct NbMo bond (3.073 $\text{A/ac>}\text{?}$;) and two bridging CO groups, one nonsymmetrically bonded through the carbon atom only (CO 1.17, NbC 2.53, MoC 2.02 $\text{A/ac>}\text{?}$;) and the other σ-bonded to Mo (MoC 1.944 $\text{A/ac>}\text{?}$;) and π-bonded to Nb (CO 1.22, NbC 2.22, NbO 2.26 $\text{A/ac>}\text{?}$;). Three types of carbonyl groups present in IV give rise to strong IR bands at 1870, 1700 and 1560 cm^?1 assigned to the terminal, μ-bridging and σ, π-bridging CO groups respectively. Complex IV has a similar structure. The electronic structure of IV and its dissociation across the NbMo bond are discussed.     

Synthesis of the 7-cis isomer of the natural leukotriene d4

Methyl 5(S), 6(S)-oxido-11-oxo-7-cis-9-trans-undecadienoate $\text{5}$ was prepared and used for the synthesis of the novel 7-cis-LTD₄ ($\text{9}$) as well as, after isomerization to the all-trans dienal ester $\text{3}$, for that of the natural leukotrienes.     

2-cyano Δ3 piperidines vi1 : a general method for the stereoselective synthesis of cis and trans 2,6-dialkylpiperidine alkaloids

The cis 2,6-dialkylpiperidine alkaloid (±) dihydro-pinidine $\text{7b}$ and the trans alkaloid (±) solenopsin A $\text{5a}$ were synthesized from a common α-aminonitrile synthon $\text{1}$. The key step in this synthesis was the stereoselective reductive decyanation of the 1-benzyl-2cyano-2′, 6-dialkylpiperidines $\text{3a}$ and $\text{3b}$.     

Regiospecific introduction of a branched-chain to kanamycin B and stereospecific transformation of the 2,6-diamino-2,6-dideoxy-D-glucopyranosyl moiety into 2,6-diamino-2,3,4,6-tetradeoxy-3-C-methyl-l-arabino or lyxo-hexopyranosyl,or 2-amino-2,3,4,6-tetradeoxy-5-C-methyl-L-threo-hexopyranosyl

4-O-(2,6-diamino-2,3,4,6-tetradeoxy-3-C-methyl-β-L-arabino and lyxo-hexopyranosyl) and 4-O-(2-amino2,3,4,6-tetradeoxy-5-c-methyl-L-threo-hexopyranosyl-6-O-(3-amino-3-decxy-α-D-glucopyranosyl)-2-deoxystreptamine ($\text{6}$, $\text{7}$ and $\text{12}$) were synthesized from a kanamycin B derivative ($\text{1}$) by regiospecific methylation and stereospecific hydrogenation followed by removal of masking groups, converting a D-sugar moiety (4-O-glycoside portion) into L-sugar. The usual conformation of $\text{6}$ and $\text{7}$ were determined as boat and skew by 250 MHz PMR spectra respectively.     

Acid - catalyzed rearrangement of butyl 2-0-acetyl-4,5-anhydro-3,6-dideoxy-hexaldonate. Synthesis of racemic epiallomuscarine and epimuscarine

Butyl 2-0-acetyl-4,5-anhydro-3,6-dideoxy-DL-xylo-hexaldonate ($\text{4}$) in the presence of SnCl₄ underwent an intramolecular rearrangement to give 2,5-anhydro ester $\text{7}$. On the other hand the lyxo epimeric epoxide $\text{5}$ under the same conditions afforded esters $\text{7}$ and $\text{8}$. Ester $\text{7}$ was transformed into racemic epiallomuscarine ($\text{12}$), whereas the isomer $\text{8}$ into racemic epimuscarine ($\text{13}$).     

Chiral synthesis of (2s,3s,7s)-3,7-dimethylpentadecan-2-yl acetate and propionate,potential sex pheromone components of the pine saw-fly neodiprion sertifer (geoff.)

A synthesis of (2S,3S,7S)-3,7-dimethylpentadecan-2-yl acetate ($\text{2}$) and propionate ($\text{3}$) is described. (2S)-2-Methyldecan-1-yl lithium ($\text{5}$) was reacted with (3S,4S)-3,4-dimethyl-γ-butyrolactone ($\text{6}$) to yield the ketoalcohol $\text{19}$ which upon Huang-Minlon reduction furnished (2S,3S,7S)-3,7-dimethylpentadecan-2-ol ($\text{1}$). Acylations gave the esters $\text{2}$ and $\text{3}$. The (2S)-2-methyldecan-1-yl lithium was obtained via asymmetric synthesis. The chiral lactone $\text{6}$ was obtained from (2S,3S)-trans-2,3-epoxybutane and dimethyl malonate.     

Nitroindolenines en serie vincadifformine : intermediaires d'acces a la vincamone et a un squelette azahomoaspidospermane

Vincadifformine and its 10-substituted analogs give in good yields 16-nitro indolenines of which the reactivity has been studied. By a two step process (demethoxycarbonylation and chloration on C16) nitro-indolenine $\text{2b}$ leads to gem-chloro-nitro $\text{6}$. By an other two step sequence (NaBH₃CN, NaH) nitro-indo-lenine $\text{2c}$ yields compound $\text{10}$ via a 16 → 1 COOCH₃ migration. By heating compounds $\text{6}$ and $\text{10}$ in CF₃COOH, rearranged products are obtained : vincamione $\text{5}$ from $\text{6}$ and azahomoaspidospermane $\text{13}$ from $\text{18}$. Mechanisms of formation of $\text{5}$, $\text{10}$ and $\text{13}$ are discussed.     

Marine natural products: fistularin-1, -2 and -3 from the sponge Aplysina fistularis forma fulva

Three new high molecular weight bromotyrosine-related metabolites, $\text{3a}$, $\text{4a}$ and $\text{5a}$, were isolated from the sponge Aplysina ( Verongia) fistularis forma fulva, and their structures were determined from high resolution ¹H NMR and other spectroscopic data. The new metabolites are formally derived by combination of major segments of two known Aplysina metabolites $\text{1a}$ and $\text{2}$.     

Flash vacuum thermolysis of spirocyclohexadienones

In an attempt to prepare short-bridged hydroxymetacyclophanes $\text{1b-d}$, the spirocyclohexadienones $\text{2b-d}$ were pyrolyzed by flash vacuum thermolysis (FVT). Instead of $\text{1b-d}$, variable amounts of 4-(5-hexenyl)phenol ($\text{4b}$), β-hydroxybenzocycloalkenes ($\text{5b-d}$) and 4-(trans-1-alkenyl) phenols ($\text{6c-d}$) were obtained. The formation of these products is explained by invoking cleavage of a spiro bond in $\text{2}$ under formation of the intermediate diradical $\text{3}$ which, depending on the length of the aliphatic chain and on the temperature, has several pathways open for isomerization to spin-paired products.     

Terpenoids of the red alga laurenciapinnatifida

The structures of three brominated terpenoids which are natural products from the red alga Laurencia pinnatifida (Gmal. Lamour) are described. The structures of the sesquiterpenes $\text{4}$ and $\text{5}$ were determined by spectral comparison and chemical interconversion. The structure of the squalene-derived terpenoid $\text{8}$ was secured by chemical transformation into thyrsiferol, a brominated triterpene previously isolated from the red alga Laurencia thyrsifera.     

Stereochemistry of nucleophilic attack by amine on a cationic π-allylnickel complex

Reaction of the π-allylnickel complex $\text{3}$ with morpholine gave a 1:1 mixture of the amines $\text{4}$ and $\text{5}$ indicating that the amine has attacked the π-allyl moiety from the side trans to nickel.