Optimizovana sinteza značajnog farmaceutskog intermedijera metil 4-[(1-oksopropil)fenilamino]piperidin-4-karboksilata

An efficient synthesis of methyl 4-[(1-oxopropyl)phenylamino]piperidine-4-carboxylate (7) has been developed starting from 1-benzylpiperidin-4-one (1). The compound is a key intermediate in the synthesis of new generation, highly active narcotic analgesics, such as remifintanil, as well as the novel classes of fentanyl analogues. An optimized Strecker-type condensation of piperidone 1 with aniline and HCN yielded the anilino-nitrile 2(≈90%) which, upon selective hydrolysis with conc. H2SO4, gave the anilino-amide 3.After vigorous basic hydrolysis of 3, followed by acidification and successive treatment with SOCl2 and MeOH, the anilino-ester 5 was obtained (40–45%, in 3 steps). N-Acylation of 5 with propionyl chloride yielded the anilido-ester 6(70–80%) In the final step, the catalytic N-debenzylation of 6 was examined under various conditions and optimized to yield 7 in near quantitative yields.U ovom radu razvijena je efikasna sinteza metil 4-[(1-oksopropil)fenilamino]piperidin-4-karboksilata (7), prolazeći od 1-benzil piperidin-4-on-1 (1). Jedinjenje 7 je ključni intermedijer u sintezi nove generacije visoko aktivnih narkotičkih analgetika, kao što je remifentanil a takođe i novih klasa analoga fentanyla. U optimizovanoj Strecker-ovoj kondenzaciji priperidona 1 sa anilinom i HCN, dobijen je anilino-nitril 2 (≈90%) prinos čijom je selektivnom hidrolizom pomoću konc. H2SO4 postao anilino-amid 3. Intenzivnom baznom hidrolizom ovog intermedijera, zakišeljavanjem a zatim sukcesivno reakcijom sa SOCl2 i MeOH sintetisan je anilino-estar 5 (≈40–45% prinos u 3 faze). N-acelovanjem anilino-estra 5 sa propionil hloridom postao je anilido-estar 6 (≈70–80% prinos). U poslednjom fazi sinteze izvršena je optimizacija katalitičkog N-debenzilovanja anilido-estra 6 do finalnog proizvoda 7, u približno kvantitativnom prinosu

Sinteza i preliminarni farmakološki testovi recemskih cis i trans 3-alkilanaloga fentanila

A general five step method for the synthesis of 3-alkylfentanyl analogues (i.e. cis and trans 3-alkyl-4-anilidopiperidines 6.1-6.6) has been developed, The starting N-phenethyl-4-piperidone 1 was first converted into the cyclohexylimine derivative 2. alpha-deprotonated with butyllithium and die resulting imine anion efficiently monoalkylated with primary, and secondary alkyl halides. After mild acid hydrolysis. the obtained 3-alkyl-4-piperidones 3.1-3.6 were isolated in good yields (79-85%), then condensed with aniline to form imines 4.1-4.6. Subsequent reduction of the imines (LiAlH4/THF) yielded cis/trans mixtures of 3-alkyl-4-anilinopiperidines 5.1-5.6. Quantitative separation of the diastereoisomers by column chromatography of Al2O3 gave pure cis 5.1-5.6 (29-51% yield) and trans 5.1-5.6 (19-27% yield), with the cis/trans ratio in the range 7/3-6/4 . The synthesis was concluded by N-acylation of the purified 5.1-5.6, with propionyl chloride, to afford cis and trans 3-alkyl-4-anilidopiperidines 6.1-6.6 (approximate to 95% yield, as monooxalate salts). No enatioseparation was attempted at any stage. The relative cis/trans stereochemistry was provisionally assigned from the H-1-NMR spectra. Of the twelve synthesized 3-alkylfentanyls. ten compounds (two known and eight novel derivatives, all as the monooxalate salts) were preliminarily tested as analgesics in rats, comparing the potency to fentanyl. Except for the known (+/-)-cis-3-Me fentanyl 6.1cis. (8 x fentanyl), and the novel (+/-)-cis-3-Et fentanyl 6.2cis. (1.5 x fentanyl), all of the others were less active than fentanyl or inactive. Some tentative conclusions on the structure-activity relationship (SAR) in this series of derivatives have been made.Razvijen je opšti metod za sintezu 3-alkil analoga fentanila (tj. cis i trans 3-alkil-4-anilidopiperidina 6.1–6.6) u pet faza. Polazni N-fenetil-4-piperidon 1 prvo je preveden u cikloheksiliminski derivat 2, α-deprotonovan butillitijumom, a postali iminski anjon efikasno monoalkilovan primarnim i sekundarnim alkilhalogenidima. Posle blage kisele hidrolize, nastali 3-alkil-4-piperidoni 3.1–3.6 izolovani su u dobrim prinosima (79–85 %), zatim kondenzovani sa anilinom do imina 4.1–4.6. Redukcijom ovih imina (LiAlH4/THF) dobijene su cis/trans smese 3-alkil-4-anilinopiperidina 5.1–5.6. Kvantitativnim hromatografskim razdvajanjem dijastereoizomera na stubu Al2O3 izolovani su čisti cis 5.1–5.6 (prinos 29–51 %) i trans 5.1–5.6 (prinos 19–27 %), gde je cis/trans odnos bio u opsegu 7/3–6/4. Sinteza je završena N-acilovanjem prečišćenih intermedijera 5.1–5.6 pomoću propionil-hlorida, pri čemu su postali cis i trans 3-alkil-4-anilidopiperidini 6.1–6.6 (prinos _ 95 %, kao monooksalatne soli). Ni u jednoj fazi nije pokušano razdvajanje enantiomera. Relativna, cis/trans, stereohemija preliminarno je određena iz 1H-NMRspektra. Od dvanaest sintetisanih 3-alkil-fentanila, deset jedinjenja (dva poznata i osam novih, sva u obliku monookasalatnih soli) preliminarno su testirana kao analgetici na pacovima, poredeći aktivnost sa fentanilom.Osim poznatog (±)-cis-3-Me fentanila 6.1 cis, (8 x fentanil), i novog (±)-cis-3-Et fentanila 6.2 cis, (1,5 x fentanil), svi ostali bili su manje aktivni ili neaktivni. Izvedeni su određeni, preliminarni zaključci u vezi odnosa strukture i aktivnosti u ovoj seriji derivata