Azomethine ylide cycloaddition/reductive heterocyclization approach to oxindole alkaloids: asymmetric synthesis of (-)-horsfiline.

The intermolecular [3 + 2] annulation of azomethine ylides with 2(2-nitrophenyl)acrylate dienophiles followed by reductive heterocyclization affords the spiro(indole-pyrrolidine) ring system. Hence, this enable us to accomplish a concise and highly enantioselective synthesis of (-)-horsfiline 1, based on chiral auxiliary-directed pi-face discrimination in the 1,3-dipolar cycloaddition of (1S,2R)-2-phenyl-1-cyclohexyl ester 4f with N-methylazomethine ylide.

Asymmetric synthesis of 2-amino-3-hydroxynorbornene-2-carboxylic acid derivatives.

The enantioselective synthesis of 2-amino-3-hydroxynorbornene-2-carboxylic acid derivatives (5) was studied using the Diels-Alder reaction between cyclopentadiene and different dienophiles, i.e., alkyl 5-oxo-2-phenyloxazol-4-methylenecarbonates (1) or 2-benzoylamino-3-alkoxycarbonyloxy-acrylates (12), operating with different Lewis acids and both with thermal and with ultrasound conditions. The enantioselective synthesis of the exo/endo compounds 5c,d and 5'c,d was achieved starting from the chiral menthyl acrylates 12b,c using Mg(ClO(4))(2) as the catalyst and ultrasound. The cycloadducts were obtained in very good yield, in mild conditions, in short time, and in good diastereomeric excess (exo, 80%; endo, 87%). Finally, the use of alkylidene-oxazolones or acrylates and EtAlCl(2) or Mg(ClO(4))(2) as the catalyst allowed control of the cycloaddition reaction in favor of the exo or endo products.

Two 17-hydroxy-9(10-->5)-abeo-estr-4-ene-3,10-diones.

(5S,9S,17S)-17-Hydroxy-9(10-->5)-abeo-estr-4-ene-3,10-dione, C(18)H(26)O(3), (II), and (5R,9R,17S)-17-hydroxy-9(10-->5)-abeo-estr-4-ene-3,10-dione, C(18)H(26)O(3), (III), are equimolecular products of the Fe(II)-induced transposition of 10beta-hydroperoxy-17beta-hydroxyestr-4-en-3-one, (I). With respect to reagent molecules, the configuration at C9 is retained for (II) while it is inverted in (III). The conformations of the five- and six-membered rings are compared.

Interactions at the outside faces of calix

Attractive pi-pi interactions between two of the four outside cavity faces of 1,3-bis-pyridylmethylcalix[4]arene (1) and both faces of 1,4-diiodotetrafluorobenzene (2a) form infinite one-dimensional non-covalent ribbons where the two modules alternate. These ribbons are cross-linked by electron donor-acceptor interactions between picolyl nitrogen atoms of calixarene 1 in one chain and iodine atoms of perfluoroarene 2a in another chain and the two-dimensional supramolecular network 3a is formed. A similar behaviour is also shown by 1,4-dibromotetrafluorobenzene (2b). The halogen bonding and the attractive pi-pi interactions occur in directions which are nearly orthogonal each other. Diiodotetrafluorobenzene, being involved in both these interactions, appears to be a particularly interesting tecton. The ability of electron-poor arenes to elicit the exo-receptor potential of calixarene module by connecting their outside faces through pi-pi interactions may be developed as a new and general binding protocol in calixarene self-assembly processes.

Access to pyrrolo- and pyrido[1,2-a]indole derivatives by intramolecular nitrone cycloadditions. Effect of steric factors on the regioselective product formation.

On starting from N-allyl-substituted 2-indolecarbaldehydes and exploiting the intramolecular nitrone cycloaddition methodology, we synthesized a number of the title fused-ring indole derivatives in racemic as well as enantiopure form.

Pyrrolidinoindoline Alkaloids from Psychotria colorata1

Fractionation of an alkaloid extract of Psychotria colorata flowers led to the isolation of six alkaloids, identified by UV, 1D and 2D NMR, and MS as (-)-calycanthine, isocalycanthine, (+)-chimonanthine, hodgkinsine, quadrigemine C, and a new alkaloid (1), whose structure was deduced by X-ray analysis to be (8-8a),(8'-8'a)-tetradehydroisocalycanthine 3a(R), 3'a(R).

Synthesis and CLOGP correlation of imidooxy anticonvulsants.

Continuing structure-activity studies on the anticonvulsant activity of analogs of N-(benzyloxy)-2-azaspiro[4.4]nonane-1,3-dione (2a), which displayed anti-electroshock seizure (MES) activity and a protective index (TD50/ED50) of > 4.5 are reported. An in-depth analysis of this moiety was studied employing the Topliss structure activity and the Craig plot analytical approaches as well as a semiempirical method. CLOG P analysis was also applied to this series after experimentally determining the NOR fragment. All compounds were minimized and these physicochemical parameters correlated to anticonvulsant activity. Several interesting substituted benzyloxy compounds emerged from this study: the 2',4'-dichloro (2b), 4'-(trifluoromethyl) (2c), 2'-bromo (2d), 3'-chloro (2o), 2'-chloro (2r), 2'-fluoro (2p), and 3'-fluoro (2w) analogs, all of which had comparable, or better activity than the parent unsubstituted analog (2a). X-ray crystal analysis of the active 2a versus inactive N-benzyl-2-azaspiro[4.4]nonane-1,3-dione (10) is discussed.