Total synthesis of optically active integerrimine,a twelve-membered dilactonic pyrrolizidine alkaloid of retronecine type. III. Regioselective elaboration of the unsymmetrical twelve-membered dilactone and total synthesis of (-)-integerrimine

The first enantioselective synthesis of optically active integerrimine, the twelve-membered dilactonic pyrrolizidine alkaloid has been achieved.     

Total synthesis of optically active integerrimine,a twelve-membered dilactonic pyrrolizidine alkaloid of retronecine type. I. Enantioselective synthesis of the protected (+)-integerrinecic acid

For the total synthesis of optically active integerrimine, the twelve-membered dilactonic pyrrolizidine alkaloid, the necic acid component (+)-integerrinecic acid has been enantioselectively synthesized in the protected form.     

Total synthesis of optically active chanoclavine-I

The total synthesis of optically active chanoclavine-I, an ergot alkaloid, was accomplished using palladium-catalyzed intramolecular cyclization (Heck reaction) as a key step. The conjugate ester (6) was obtained in 2 steps from optically active 4-bromotryptophan (10), and the cyclization of 6 proceeded smoothly without racemization to give the key intermediate, tricyclic tetrahydrobenz[c,d]indole derivative (7), in high yield.     

First total synthesis of a new pyrrolizidine alkaloid, amphorogynine A

An efficient and stereodefined strategy is described for the first asymmetric synthesis of a new type of pyrrolizidine alkaloids, amphorogynine A and its 1-epi-isomer. The key 2,4-disubstituted pyrrolidine ring was constructed by elaboration of the chiral lactam derivative incorporating the d-malic acid-derived skeleton through asymmetric cis-allylation of the functionalized allysilane.     

Synthesis and properties of optically active phosphine-boranes possessing an l-menthyloxy group

(SP)-9-Anthryl(l-menthyloxy)phenylphosphine-borane and (SP)-(1-l-menthyloxy)benzo[b]phosphole-borane were synthesized, and their structures were characterized by X-ray crystallographic analysis. The latter compound was reduced by lithium naphthalenide at −78°C with cleavage of the P O bond, and the subsequent reaction with electrophiles afforded the corresponding tertiary phosphine-boranes possessing good to excellent enantiomeric excesses.     

A nitrone-based synthesis of the pyrrolizidine alkaloid croalbinecine

A highly stereoselective and efficient nitrone-based synthesis of dl-croabinecine is recorded herein     

Total synthesis of a macrocyclic spermidine alkaloid,codonocarpine

Total synthesis of codonocarpine ($\text{5}$) and its regio-isomer ($\text{1}$$\text{5}$) utilizing a new cyclization procedure is described.     

NMR studies of inclusion complexation of the pyrrolizidine alkaloid retronecine and p-sulfonic acid calix[6]arene

Accidental or intentional drug toxicity in humans and animals is a major concern and the search for detoxificant agents is a challenge. Pyrrolizidine-producing forages are a threat not only to livestock, but also to humans as a consequence of food contamination. Supramolecular systems are promising as detoxificant agents by decreasing the bioavailability of toxic compounds in biological environment. Cyclodextrin and calix[n]arenes are well known hosts for a variety of molecules and/or ions. Surprisingly, only few studies describe the potential of calix[n]arenes as host for toxic molecules. This study focused on the use of NMR techniques as tools for the investigation of the interactions between p-sulfonic acid calix[6]arene and retronecine, a toxic pyrrolizidine alkaloid.     

Total synthesis of optically active myo-inositol 1,4,5-tris(phosphate)

Optically active myo-inositol 1,4,5-tris(phosphate) has been synthesized starting from myo-inositol.     

Ligularidine,a new pyrrolizidine alkaloid from Ligularia dentata

The structure of a new macrocyclic pyrrolizidine alkaloid, ligularidine(1), having significantly high mutagenic activity was elucidated and the configurations of the necic acid and its enantiomer reported by Edwards² were also determined.     

Senecicannabine,a new pyrrolizidine alkaloid from senecio cannabifolius

The structure of senecicannabine($\text{1}$), a new mcrocyclic pyrrolizidine alkaloid isolated from $\text{Senecio cannabifolius}$, has been established by chemical study and X-ray analysis.     

Total synthesis of optically active liverwort sesquiterpenes,trifarienols A and B,using phenylethylamine as a chiral auxiliary

The imine of (rac)-2,3-dimethylcyclohexanone 10a with (S)-(−)-phenylethylamine was reacted with methyl acrylate to yield methyl (1′S,6′R)-3-(1′,6′-dimethyl-2′-oxocyclohexyl)propanoate 4a in 26% (97% ee) after hydrolysis. When (2RS,3R)-2,3-dimethylcyclohexanone 10b was used, the same product 4b was obtained in 59% yield (>99.5% ee) after hydrolysis. When (2RS,3R)-2,3-dimethylcyclohexanone 10b and (R)-(+)-phenylethylamine were used, the reaction underwent in only 5% yield, the products being 4c, 12, 13, 14, and 15. Thus, the reaction of 3b with methyl acrylate is a matched case, while that of 3c is a mismatched case. These phenomena are explained by the nonbonded interaction of methyl acrylate with chiral phenylethylamine and the methyl group at the 6′-position of the cyclohexanone ring in the transition state. The propanoate product 4b was successfully transformed into liverwort sesquiterpene (+)-trifarienol A 1 and (−)-trifarienol B 2 in 10 steps. We have developed an HPLC method to determine the ees of 2,2-disubstituted and 2,2,3-trisubstituted cyclohexanones using the corresponding pentafluorophenyl esters.     

Total synthesis of amaryllidaceae alkaloid buflavine

A concise synthesis of the amaryllidaceae alkaloid buflavine (1) and its regioisomer (2) involving sequential Meyers' biaryl coupling, enecarbamate formation, and hydrogenation followed by ultimate intramolecular reductive amination is presented.     

光学活性姜黄烯化合物的立体选择性合成

本文报道了在手性膦过渡金属配合物催化下,以对溴甲苯与6-甲基-5-庚烯-2-溴化镁(5)经不对称交叉偶联反应合成(R)-(-)-和(S)-(+_)-α-姜黄烯的方法,光学收率分别为44%e.e和50.3%e.e.(R)-(-)-α-姜黄烯经Birch还原得到(R)-(-)-β-姜黄烯.对溴苯甲醚经不对称交叉偶联、Birch还原等反应合成了(S)-(+)-γ-姜黄烯.