Synthesis and properties of 3′-deoxyadenylate trimer dA2′p5′A2′p5′A

The trimeric 3′-deoxyadenylyl-(2′→5′)-3′-deoxyadenylyl-(2′→5′)-3′-deoxyadenosine ($\text{1}$$\text{2}$) was synthesized via the phosphotriester approach starting from cordycepine ($\text{1}$). Various physical data have been determined and compared with those of the ribo-A2′p5′A2′p5′A analog.     

Two chrome derivatives from the brown alga Zonariatournefortii

Two minor lipid components of the brown seaweed $\text{Zonaria}$$\text{tournefortii}$ were characterized as (all Z) - 5′,7′-dihydroxy-2′-nonadeca-4,7,10,13,16-pentenyl-chrome chromone ($\text{3}$) and 5′,7′-dihydroxy-2′-pentadecylchrome ($\text{4}$).     

A novel deaminative cyclization of aminoglycoside. Synthesis of a kanamycin B variant having 2-oxa-5-azabicyclo[2,2,2]oct-1,5-diene ring

The 3′,5′-diene derivative of kanamycin B ($\text{2}$) was obtained from a 4′-ene derivative of kanamycin B ($\text{1}$) by treatment with trimethyl orthoacetate. Formation of the title compound ($\text{4}$) from $\text{2}$ deaminative cyclization with sodium methoxide followed by treatment with trifluoroacetic acid was described.     

Successive methyl migrations occurring in the acid treatment of 1-epoxyethyl-1,2,2-trimethyl-cyclopentane derivative

Acid treatment of (IR, 3S,1′S)-1-(1′,2′-Epoxyethyl)-1,2,2-trimethyl-3-acetoxymethyl-cyclopentane $\text{6}$) has been shown to yield three products ($\text{8}$, $\text{9}$, $\text{10}$), among which $\text{8}$ and $\text{9}$ are 1-oxa-bicyclo[3.3.0]octane derivatives formed $\text{via}$ successive methyl migrations followed by an oxorane ring closure.     

Substituted cyclononatetraenes and nonafulvenes

Reaction of $\text{cis}$,$\text{cis}$,$\text{cis}$,$\text{cis}$-[9]annulene anion ($\text{1}$) with electrophiles ($\text{2a}$-$\text{d}$) leads to substituted $\text{cis}$,$\text{cis}$,$\text{cis}$,$\text{cis}$-1,3,5,7-cyclononatetraenes ($\text{3a}$-$\text{d}$) which are precursors for the preparation of 10- and 10,10′-donor-substituted nonafulvenes (e.g. $\text{7b′}$$\text{e′}$). The influence of solvent and temperature on the ¹H-nmr spectra of the nonafulvenes $\text{7b′}$-$\text{h′}$ has been investigated.     

A general synthesis of side chain derivatives of Δ9-thc

The synthesis of (6aR, 10aR)-trans-3-[1′,3′-dithian-2′-yl]-6a,7,8,10a-tetrahydro-6,6,9- trimethyl-6H-dibenzo[b,d]pyran-l-ol t-butyldimethylsilyl ether ($\text{4b}$) is reported. The use of this compound as a source of side chain derivatives of cannabinoids is illustrated by syntheses of 1′-,2′-,3′- and 4′-hydroxy-Δ⁹-THC, and 3-carboxy-6,6,9-trimethyl-6H-dibenzo[b,d]pyran-1-o1 ($\text{6}$).     

Adenosine cyclic 3′,5′-(RP)- and (SP)-phosphoramidates,the first representatives of nucleoside cyclic 3′,5′-phosphoramidates derived from ammonia

Adenosine cyclic 3′,5′-phosphoramidate $\text{2}$ was synthesized by reacting adenosine cyclic 3′,5′-phosphate $\text{1}$ with POCl₃, in trimethyl phosphate for 1 h at O°C, followed by in situ treatment of the reaction mixture with a suspension of (NH₄)₂CO₃ in anhydrous DMF or pyridine or DMF/pyridine mixture for 30 min at 25° C. Diastereoisomers ($\text{R}$_P)-$\text{2}$ and ($\text{S}$_P)-$\text{2}$ the relative quantities of which depended on the solvent of (NH₄)₂CO₃ treatment, were separated by reversed phase partition chromatography. Hydrolysis of (R_P)-$\text{2}$ and (S_P)-$\text{2}$ proceeded with predominant (90% in 0.1 N HCl, 100% in 0.1 N NaOH) -P-O-C bond breaking.     

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.     

Herpetetradione,nouveau lignoide tetramere isole d'Herpetospermum caudigerum wall.

The title compound, a new tetramer of coniferyl alcohol, has been isolated from seeds of $\text{Herpetospermum caudigerum}$ Wall. (Cucurbitaceae). Its structure was elucidated by spectroscopic means as $\text{rel}$-(7′S, 8′S, 7″S, 8″)-4,9,4′,4″,4″′,9″′-hexahydroxy-5,5′5″,5″′-tetramethoxy-7,7″′-dioxo-8.3′, 7′.0.9″,8′.8″,9′.0.7″,3″.8″′ -lignoïd.     

Stéréosélectiveté de la condensation aldolique. Réaction du benzaldéhyde et d'énolates carbéniates magnésiens α-chlorés

Alkyl chloracetates III (R′ = H) and phenylchloracetates III (R′ = Ph) condense with PhCHO in the presence of (i-Pr)₂NMgBr giving alkyl-2-chloro-3-hydroxy-3-phenyl propionates (RS, RS) (I) and (RS, SR) (II) in equal ratio ($\text{1}\text{1}$) for III (R′ = H) and in the ratio $\text{65}\text{35}$ for III (R′ = Ph) irrespective of the group R. When the same reaction is performed with alkyl chloropropionates III (R′ = CH₃) the isomer ratio is dependent upon the group R. These results are interpreted by considering a planar (R′ = H or Ph) or pyramidal (R′ = CH₃) geometry of the intermediate enolate-carbeniate.     

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.     

Novel nucleoside analogues via direct attack of carbon : Nucleophiles on nucleosides containing epoxy-sugars

Direct ring-opening of the epoxide ring in 1-(5′-$\text{O}$-trityl-2′,3′-anhydro-β-D-lyxo-furanosyl) uracil (1) by lithium acetylide or vinylmagnesium bromide/cuprous iodide affords the corresponding 5′-$\text{O}$-trity]-3′-$\text{C}$-substituted-3′-deoxy-$\text{ara}$-uridine species.     

Stekeospecific transformation of D-sugar to L-sugar in complex aminoglycoside. Synthesis of a kanamycin B analog having 2,6-diamino-2,4,6-trideoxy-L-arabino-hexopyranose

A 4′-ene derivative of kanamycin B ($\text{4}$) was derived from the epoxide ($\text{1}$) by oxidative elimination of the 4′-phenylseleno group into the allylic alcohol ($\text{3}$). The title compound, 0-(2,6-diamino-2,4,6-trideoxy-β-L-arabino-hexopyranosyl)-(1→4)-0-[3-amino-3-deoxy-α-D-glucopyranosyl-(1→6)]-2-deoxystreptamine ($\text{6}$) was obtained from $\text{4}$ by stereospecific hydrogenation followed by removal of the masking groups, changing the D-sugar moiety of the 4-0-glycoside portion into an L-sugar.     

Stereochemical consequence in the elimination of β-hydroxyalkylsilanes: Stereoselective formation of (Z)- and (E)-alkylidene-γ-butyrolactones

Titanium(IV) chloride-mediated reaction of 4,5-dihydro-2-(trimethylsiloxy)-3-(trimethylsilyl)furan (1a) with acetaldehyde gave $\text{diastereomerically pure}$ (3S^*, 1′R^*)-4,5-dihydro-3-(1′hydroxyethyl)-3-(trimethylsilyl)-2(3$\text{H}$)furanone (2a), which afforded selectively either (Z)- or (E)-α-ethylidene-γ-butyrolactone (3a) under proper conditions. Facile isomerization of 2a into $\text{diastereomerically pure}$ (3S^*, 1′R^*)-4,5-dihydro-3-&{1′-(trimethylsiloxy)ethyl}-2(3$\text{H}$)furanone (4) suggests an intriguing stereochemical outcome from 2a to (E)-3a via an enolate of 4.     

The chemical synthesis of the RP and SP diastereomers of thymidyl(3′-5′)thymidyl 0,0-phosphorothioate

The synthesis and separation of diastereomere of protected thymidyl(3′–5′)thymidyl 0,0-phosphoranilidate ($\text{4}$) allowed to obtain in the stereospecific manner title compounds $\text{5}$, whose absolute configuration at P atom was assigned enzymatically. T_P(S)T diastereomers ($\text{5}$) were obtained independently via “phosphite” procedure.     

Simple,inexpensive routes to E and Z zeatine ribosides and derivatives useful for immunoassay.

Allylic oxidation of 6-$\text{N}$-(3,3-dimethylallyl)adenosine $\text{1}$ gave $\text{trans}$ ($\text{E}$) zeatine riboside $\text{3}$, which was isomerized to the $\text{cis}$ ($\text{Z}$) isomer $\text{5}$ by u.v. irradiation. A method for the regiospecific 3′-$\text{O}$-succinoylation of these nucleosides is given.     

Diethyl[trimethylsilylethoxymethyl]phosphonat - ein neuartiges reagens für variable aufbaustrategien von carbonyl-, α-hydroxycarbonylverbindungen und vinylphosphonaten

The carbanion of $\text{2}$ prepared by means of s-BuLi can be transformed stepwise with various electrophiles to the phosphonates $\text{3}$–$\text{5}$, opening via $\text{6}$ new approaches to carbonyl compounds $\text{7}$, phosphates of α-hydroxycarbonylderivatives $\text{8}$ and vinylphosphonates $\text{9}$.     

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 $\text{7}$.     

(+)- and (-)-1-0, 4-0-bis(p-chlorobenzyl)threitol as novel resolving agents for optically active anthracyclinone synthesis: an efficient synthesis of optically pure 4-demethoxydaunomycinone

(±)-7-Deoxy-4-demethoxydaunomycinone(±)-$\text{3}$) was cleanly resolved by forming a mixture of the diastereomeric acetals ((?)-$\text{9}$ and (+)-$\text{10}$ or (+)-$\text{9}$ and (?)-$\text{10}$ with the title $\text{vicinal}$-diol((+)- or (?)-$\text{5}$) to give optically pure (R)(?)-$\text{3}$. The method for racemizing the undesired enantiomer((S)(+)-$\text{3}$) was also explored. Optically pure (+)-4-demethoxydauno-mycinone ((+)-$\text{2b}$) was elaborated from (R)(-)-$\text{3}$ according to the reported reaction scheme.     

Etude de l''addition des organomagnesiens satures et benzyliques aux enynes conjugues, simples et fonctionnels

Saturated and benzylic organomagnesium compounds are shown to readily undergo addition reactions with the conjugated enynes H$\text{C}\text{4}$$\text{C}\text{3}$C$\text{H}\text{2}$$\text{C}\text{1}$HCH₂R′, with R′ = alkyl, OH, OC₄H₉, NHC₂₅, N(C₂H₅)₂, by refluxing for several hours in benzene or toluene.This reaction leads to both υ-acetylenic compounds (1,2-addition) and β-allenic compounds (1,4-addition).