13C and1H NMR spectra of spiropiperidine alkaloids of Nitraria

A detailed interpretation is given of the¹³C and¹H NMR spectroscopy of the spiropiperidine alkaloids of the nitramine group, and the results are generalized. The assignment has been made of the carbon-13 resonance lines in the spectra of five natural compounds. A dependence of the parameters on the spatial structures of the compounds of this series has been found. The overall PMR spectra of seven natural alkaloids and some of their derivatives are discussed. The conformations of acyl derivatives have been established.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 82–91, January–February, 1988.     

Quantum-chemical study of the spiropiperidine alkaloids ofNitraria I. Intramolecular hydrogen bonds and chemical properties of nitramine and isonitramine

Preferential conformations have been found for nitramine and isonitramine on the basis of quantum-chemical calculations of various conformational states. The results obtained have been correlated with spectral characteristics and chemical properties.Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 897–902, November–December, 1996. Original article submitted May 6, 1996.     

Diasteroselective synthesis of new spiropiperidine scaffolds from the CN(R,S) building block

A methodology allowing the construction of spiropiperidine scaffolds similar to those found in naturally occurring alkaloids has been developed. This approach begins with the well-established CN(R,S) strategy, the spiro-center being built by way of an intramolecular attack of a nitrile function by an organolithium species obtained by a halogen/lithium exchange reaction mediated by either t-BuLi or lithium naphthalenide.     

手性炔基亚砜作为二碳合成子在生物卤介不对称合成中的应用

本文报导了手性炔基亚砜的制备及其在四氢异喹啉及四氢咔啉生物碱对映体选择性合成中的应用。     

Synthesis of functionalized azadienes from aminobenzothiazole, acetylenic esters and isocyanides

The reaction between 2-aminobenzothiazole with dialkyl acetylenedicarboxylates in the presence of isocyanides,leads to functionalized azadienes in good yields.     

First syntheses of two quinoline alkaloids from the medicinal herb Ruta chalepensis via cyclization of an o-iodoaniline with an acetylenic sulfone

The first syntheses of two quinoline alkaloids found in the medicinal herb Ruta chalepensis are reported via the conjugate addition of an o-iodoaniline to an acetylenic sulfone, followed by Pd-catalyzed carbonylation, intramolecular acylation of the corresponding sulfone-stabilized carbanion, and reductive desulfonylation.     

Carbonyliron Complexes of Allenic Acids,Esters, Amides,and Imides

On irradiation in the presence of Fe(CO)₅, the allenic amides and imides showed a similar course of complexation to that of esters and lactones, respectively, e.g. the amides of type 10 led to diiron complexes of type 11 (Scheme 3), whereas the imide 12 yielded a mixture of a dinuclear and two mononuclear complexes ( 13–15 , Scheme 4). The racemic ester 6 also gave mononuclear ( 7a , 7b , and 9 ) and dinuclear complexes (8 a and 8b ; Scheme 2). In case of the allenic acid 4 , only complexation of type 5 was observed (Scheme 1).     

Efficient synthesis of highly substituted thiophenes from acetylenic esters, ethyl bromopyruvate, and tetramethylthiourea

The reaction of acetylenic esters with ethyl bromopyruvate in the presence of tetramethylthiourea led to highly functionalized thiophenes in excellent yields.     

Efficient synthesis of highly substituted thiophenes from acetylenic esters,ethyl bromopyruvate,and tetramethylthiourea

The reaction of acetylenic esters with ethyl bromopyruvate in the presence of tetramethylthiourea led to highly functionalized thiophenes in excellent yields. Correspondence: Issa Yavari, Chemistry Department, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran.     

Rearrangements of the Diels-Alder cycloadducts obtained from acetylenic sulfones and 1,3-diphenylisobenzofuran

1,3-Diphenylisobenzofuran afforded Diels-Alder cycloadducts 4a,b with n-butyl- and phenyl-substituted acetylenic sulfones 3a,b, respectively. The products underwent various types of rearrangements under pyrolytic, acid-catalyzed, and photochemical conditions. In the presence of acid, or upon heating in xylenes, they afforded the ketones 5a,b. In addition, the dehydration product 7a was produced from the pyrolysis of 4a, and the unexpected transposed ketone 6b was generated under acid-catalyzed or pyrolytic conditions from 4b via a postulated epoxide intermediate. The photolysis of 4a afforded ketone 5a as the sole isolated product, whereas 5b afforded oxepin 8b and indenyl phenyl ketone 9b. The formation of the latter two products can be rationalized by a series of pericyclic reactions. These include an intramolecular [2+2] cycloaddition, followed by a 1,3-dipolar cycloreversion, for the transformation of 4b to 8b and a series of electrocyclic and [1,3]sigmatropic reactions to convert 8b into 9b.