Naresh V. Mody

13C nuclear magnetic resonance spectroscopy of atisine and veatchine-type C20-diterpenoid alkaloids from aconitum and garrya species

Abstract 13 C NMR spectra of the atisine- and veatchine-type alkaloids, as well as certain of their derivatives, have been obtained by the Fourier transform technique at 25.03 MHz. With the help of single-frequency off-resonance proton decoupling techniques, additivity relationships, and the effects induced by certain structural changes, self-consistent assignments of nearly all the resonances have been made. The 13 C NMR spectra are also analyzed to identify skeletal features of the atisine and veatchine-type alkaloids of use in the structure determination of new C 20 -diterpenoid alkaloids. On the basis of the 13 C NMR analysis of atisine and veatchine as well as a temperature-dependence study of atisine, the existence of C-20 epimers in these alkaloids is demonstrated. A 13 C NMR study of the behavior of the oxazolidine ring of atisine in non-ionic and ionic solvents indicates that the C-20 epimers of atisine do not exist in an equilibrium mixture in solution and are not interconvertible via a zwitterion as reported earlier.

An alumina catalyzed addition of secondary amines to exocyclic α,β-unsaturated ketones

Abstract A Michael addition of secondary amines to exocyclic α,β-unsaturated ketones has been achieved in excellent yield in the presence of alumina. In the absence of alumina, the reaction does not proceed or takes place in low yield with many side products after a long reaction time.

The structure and absolute configuration of heterophylloidine

Abstract The structure and absolute configuration of heterophylloidine, a new C 20 -diterpenoid alkaloid isolated from Aconitum heterophylloides Stapf, have been determined with the aid of 13 C NMR spectral data and single-crystall X-ray analysis of the product obtained by treatment of heterophylloidine with aqueous hydrobromic acid.

An unusual oxidation of an NCH3 group to an NCHO group by osmium tetroxide

Treatment of pyrodelphinine ( 1 ) with osmium tetroxide afforded a mixture of the cis-hydroxylation product 2 and an unexpected product 3 in the ratio of 4:1, respectively. Similarly, oxidation of delphinine ( 5 ) afforded α-oxodelphinine ( 6; 75%) and oxidation of mesaconitine ( 8 ) furnished oxonitine ( 9; 92%). Thus a very selective oxidation of the N-methyl group of delphinine and mesaconitine is effected osmium tetroxide.

The alkaloids of nutt.

The structures of alkaloid- and - were established via X-ray crystallography of the former as its HI salt, and its chemical conversion to the latter.Abstract The structures of alkaloid- A and - B were established via X-ray crystallography of the former as its HI salt, and its chemical conversion to the latter.

A Convenient Method for Constructing Oxazolidine and Thiazolidine Rings in C20-Diterpenoid Alkaloid Derivatives

Abstract Recently we isolated and elucidated1 the structures of two new C20-diterpenoid alkaloids, lindheimerine (1) and ovatine (2), from Garrya ovata var. lindheimeri. To correlate lindheimerine with ovatine and to prepare some new oxazolidine and thiazolidine ring-containing analogs from the imine-containing derivatives for biological testing and spectral studies, we required a simple, high-yield method for constructing these rings. The earlier method reported2 for constructing the oxazolidine ring from the imine derivative requires the use of a quaternization reaction involving ethylene chlorohydrine in dimethylformamide at 80°C.

A reinvestigation of the structures of acomonine, iliensine, 14-dehydroiliensine, and 14-benzoyliliensine

Abstract The novel structures assigned by Yunusov et al to the C 19 -diterpenoid alkaloids, acomonine ( 1 ), iliensine ( 2 ), 14-dehydroiliensine ( 3 ), and 14-bensoyliliensine ( 4 ) have been found to be in error. We have demonstrated that these alkaloids are identical with the well-known alkaloids, delsoline ( 5 ), delcosine ( 6 ), 14-dehydrodeloosine ( 7 ), and 14-benzoyldelcosine ( 8 ), respectively.

Sodium cyanoborohydride: a reagent for selective reduction of the oxazolidine ring of C20-diterpenoid alkaloids

Abstract A very selective reduction of the oxazolidine ring of C 20 -diterpenoid alkaloid derivatives in the presence of other functional groups, e.g., an α,β unsaturated ketone or a simple ketone, has been achieved in almost quantitative yield using sodium cyanoborohydride.

Construction of “normal”- and “iso-type” oxazolidine rings in C20-diterpenoid alkaloids: Oxidative cyclization with potassium ferricyanide

Abstract An efficient and simple method using alkaline ferricyanide for converting the NCH2CH2OH group-containing alkaloid derivatives into their “normal”- and “iso-type”-oxazolidine ring-containing alkaloids has been developed. This is the first one-step oxidation method which affords both types of oxazolidine rings simultaneously.

Chapter 1 The Structure and Synthesis of C19-Diterpenoid Alkaloids

Publisher Summary Since the early 1800s, the alkaloids (nitrogenous organic bases) isolated from plants of the Delphinium and Aconitum genera (Ranunculaceae) and more recently the Garrya genus (Garryaceae) and Inula royleana (Compositae) have been of interest because of their pharmacological properties, complex structures, and interesting chemistry. Biogenetically, these diterpenoid alkaloids are possibly formed in nature from tetracyclic or pentacyclic diterpenes in which the nitrogen atom of β -aminoethanol, methylamine, or ethylamine is linked to C-19 and C-20 in the C 20 -diterpenoid skeleton and C-17 and C-19 in the C 19 -diterpenoid skeleton to form a substituted piperidine ring. These diterpenoid alkaloids may be divided into two broad groups: those based on a hexacyclic C 19 -skeleton, and those based on a C 20 -skeleton. The C 19 -alkaloids are commonly called aconitines, and all possess the aconitine, the lycoctonine, or the heteratisine skeleton. Usually in the literature, the C 19 -diterpenoid alkaloids are referred to as either aconitinetype or lycoctonine-type alkaloids without structural differentiation. This practice sometimes creates confusion, therefore, this chapter has divided the C 19 -diterpenoid alkaloids into three categories, defined as follows: (1) Aconifine-type ; (2) Lycoctonine –type ; and (3) Heterutisine-type. These alkaloids possess the skeleton of heteratisine, in which a lactone moiety is always present.