Anna Diez

New synthesis of benzo [a]quinolizidin-2-ones via protected 2-aryl-4-piperidones

Abstract A new synthesis of 9,10-dimethoxy-1,3,4,6,7,11b-hexahydro-2H-benzo aquinolizin-2-one ( 1a and its 3-ethyl derivative 1b via the corresponding 2-(3,4-dimethoxyphenyl)-4-piperidone ethylene acetals 7 is reported. Alkylation of 2-arylpipendires 7 with 2-bromoethanol followed by oxidation of the resulting amino alcohols 9 with oxalyl chloride and dimethyl sulfoxide afforded the aldehydes 10 , which were cyclized with hydrochloric acid to give 7-hydroxybenzo[α]quinolizidines 11 . The reduction of 1 with trinethylsilane and subsequent acid hydrolysis led to benzo aquinolizidin-2-ones 1 .

Synthetic applications of 2-(1,3-dithian-2-yl)indoles VI.1 Synthesis of 20-epidasycarpidone

Abstract 20-Epidasycarpidone ( 10 ) and its N -benzyl analogue 9 have been synthesized via a conjugate addition of 2-(1,3-dithian-2-yl)indole ( 6 ) and 3-ethyl- Δ 3 -piperidein-2-ones 7 and 8 , respectively. The transformation of 20-epidasycarpidone to 20-epiuleine ( 11 ) has been carried out as described in the literature in order to corroborate the structural assignments.

Synthetic applications of 2-(1,3-Dithian-2-yl)indoles V.1 asymmetric synthesis of dasycarpidone-type indole alkaloids

Chiral tetracyclic dasycarpidone-type compounds (αR, 1S, 5R)-4 and (αR, 1R, 5S)-16 have been synthesized from 2-(1,3-dithian-2-yl)indole 6 and (αR)-N-(β-hydroxy-α-phenylethyl)-Δ3-piperidein-2-one8 in three steps, following the methodology that we described recently.

Synthetic applications of 2-(1,3-dithian-2-yl)indoles. IV: New synthesis of the tetracyclic ABED ring system of Strychnos alkaloids

Abstract A new and versatile synthesis of tetracyclic compounds 10, 22 and 24 presenting the ABED ring system of Strychnos alkaloids is described by closure of the C1C11b bond in the key step. The intermediate tetrahydropyridinium salts 2 have been obtained from 2-(1,3-dithian-2-yl)indole (3) and either 2-cyano-3-ethyl-1-methyl-1,2,3,6-tetrahydropyridine (4a) or N-substituted Δ3-piperidein-2-ones (5).

Use of dioxiranes for the chemoselective oxidation of tertiary amines bearing alkene moieties

A neat and high yield chemoselective epoxidation of alkene moieties present in tertiary amines is accomplished by treatment of the corresponding amine–boron trifluoride adduct with dimethyldioxirane or methyl(trifluoromethyl)dioxirane.

3-Amino-2-piperidones as constrained pseudopeptides: Preparation of a new Ser-Leu surrogate

Abstract We describe a stereoselective preparation of 3-amino-2-piperidone 1 , a new conformationally constrained Ser-Leu surrogate. The key steps of the synthesis of compound 1 are the lactamisation of the secondary aminolactone 4 and the amination of the 3-position via the sulfite 2 .

Conformationally restricted analogues of methionine: Synthesis of chiral 3-Amino-5-methylthio-2-piperidones

Abstract (αR, 3RS, 5S)-3-Amino-N-(2-hydroxy-1-phenylethyl)-5-methylthio-2-piperidones1 have been synthesized from enamide 2 by subsequent free radical addition of methanothiol on position 5 and amination of 3-position.

Aminoimidazo[1,2-a]pyridines: regioselective synthesis of substituted imidazonaphthyridines, azacarbolines and cyclazines

Abstract In order to study the regioselectivity of thermal cyclocondensation, aminoimidazo[1,2-a]pyridines (AIP) 5a–e were prepared, further converted into iminophosphoranes 7a–e , and ultimately converted regioselectively in angular annulated imidazonaphthyridines (IN) 8a , 10a , 11a , 12a or linear annulated dipyridoimidazole (DPI) 17a . From 2-substituted derivative 23 , the peri annulated product 24a was obtained. The starting amines 5a–f reacted with aldehydes to yield regioselectively IN 8a–c , 10a–c , 11a–c , 12a,b , DPI 16a–e , 17a–d and TIBO like structures (±)-13 and 24a–c , as proved by X-ray analysis. The 1,2- or 1,4-addition between amines and α,β-unsaturated aldehydes concerning the pyridine and imidazole moieties is discussed in the light of these results.

Synthesis of a 3-aminopiperidin-2,5-dione as a conformationally constrained surrogate of the Ala-Gly dipeptide

Abstract The preparation of the Boc-{Ala-Gly}-OBn pseudopeptide 4 is reported. The key intermediate, aminoester 5b, was obtained by a cross-coupling reaction of alaninezinc iodide 6 and the thioester of glycine 9.

Synthetic studies on indole alkaloids. III. Synthesis of 1-ethylindolo[2,3-a]quinolizidin-2-one☆

Abstract The synthesis of 1-ethylindolo[2,3- a ]quinolizidin-2-one 3 is reported by potassium tert -butoxide cyclization of N -hydroxyethyl-2-[1-(phenylsulfonyl)-3-indolyl]-4-piperidone ethylene acetal 10 followed by acid treatment of the intermediate spiroindolenines 8 .