Derek J. Simmonds

Alkaloids of catha edulis(khat). Part 1. Isolation and characterisation of eleven new alkaloids with sesquiterpene cores (cathedulins); identification of the quinone–methide root pigments

Extraction of fresh and dried specimens of Catha edulis(khat) originating from Ethiopia, Kenya, and the Yemen, has led to the isolation of eleven new celastraceous alkaloids having molecular weight of ca. 600—ca. 1 200 and a sesquiterpene core. They fall into three groups: (a) cathedulins E2 and E1, esters of a pentahydroxydihydroagarofuran; (b) cathedulins K1 (Y1), K2, K6, and K15, esters of euonyminol a nonahydroxyagarofuran, containing one dilactone bridge; and (c) cathedulins E3(K11), E4, E5, E6, and K12, more complex esters of euonyminol containing two dilactone bridges.Apart from norpseudoephedrine (cathine) and the corresponding ketone (cathinone) and a related pyrazine, khat contains steroids and triterpenes including, in the root-bark, a range of triterpenoid quinonemethides characteristic of the Celastraceae.

Structural and solvatochromic studies of a series of tricyanoquinodimethane-based zwitterions

The synthesis and characterization of three new solvatochromic tricyanoquinodimethane zwitterionic systems is reported. (Z)-{β-[N-(1-Propyl)benzothiazolium-2-yl]-α-cyano-4-styryl}dicyanomethanide, C3H7(2)BT3CNQ, (Z)-{β-[N-(1-propyl)benzothiazolium-2-yl]-α-cyano-4-(2,3,5,6-tetrafluorostyryl)}dicyanomethanide, C3H7(2)BT3CNQF4, and (Z)-{β-[N-(1-butyl)benzoselenazolium-2-yl]-α-cyano-4-styryl}dicyanomethanide, C4H9(2)BS3CNQ, exhibit negative solvatochromism, consistent with a transition from an ionic ground state to a significantly less polar excited state. X-Ray crystallography measurements confirm the zwitterionic ground state of these novel T3CNQ-based chromophores. The solvatochromic properties of these compounds are compared to those of a series of related quinolinium/pyridinium adducts, and also with those of the Reichardt betaine dye.

The synthesis of long-chain unbranched aliphatic compounds by molecular doubling

A convenient General synthesis, applicable to alkanes and terminally mono- and di-substituted alkanes of any chain length, is described; cyclododecanone is used as the starting material, and the C12 chain is doubled in length as often as required and adjusted first to a multiple of 12, and than to any desired length.

Langmuir–Blodgett film forming properties of substituted TCNQ molecules

Abstract The synthesis of the zwitterionic D- π -A TCNQ adduct Z- β -(1-hexadecyl-2-quinolinium)-α-cyano-4-styryldicyanomethanide (C 16 H 33 (2)-Q3CNQ) has been performed for the Langmuir–Blodgett film deposition. The molecules in the floating Langmuir film are believed to lie at an angle of 19° to the water subphase. Optical absorption in the Langmuir–Blodgett films shows that the material is solvatochromic. The angle of molecular stacking in the Langmuir–Blodgett film is found to be 32° from surface plasmon measurements.

Thermotropic Side Chain Liquid Crystal Polymers

A simplified representation of a polymer containing lath-like, side chain substituents is shown in Fig. 7.1(a) (cf. Table 1.1 in Chapter 1); the term ‘comb polymer’ is an attractive description for this type of structure. Each repeating unit contributes a short length of the comb’s spine and one tooth. As long as the motions of the polymer backbone do not unduly restrict the freedom of mesogenic teeth to form ordered assemblies, then we might expect such materials to reproduce, to some degree at least, any liquid crystal (LC) behaviour associated with the mesogen units as small-molecule liquid crystals (SMLCs). We have then a model for comb liquid crystal polymers (comb LCP) or side chain liquid crystal polymers (SCLCPs).1

Alkaloids of Catha edulis. Part 4. Structures of cathedulins E3, E4, E5, E6, and K12. Novel sesquiterpene alkaloids with mono- and bismacrolide bridges

Alcoholysis and reduction shows that cathedulin E3, C54H60N2O23, is made up of a euonyminol core (3)(octaacetate), together with four acetates, a hydroxyisobutyrate, and evoninate (1) and cathate residues. The latter, a novel residue, is shown to be (4). By study of 1H and 13C n.m.r. data for the intact alkaloid and its hydrogenolysis and partial methanolysis produces, E3 is formulated as (12). Cathedulin E4, converted into E3 by acetylation, is (13). Corresponding to both alkaloids is a minor series in which one acetate is replaced by a benzoate residue.Cathedulin E6, C57H62N2O22, formulated as (17), is also based on a euonyminol core but gives, on methanolysis, dimethyl evoninate, methyl benzoate, methyl nicotinate, and trimethyl gallate; a 2-acetoxyisobutyrate and a further acetate residue are also present. Alkaloid E6 bears to E5 (16) the same relationship as does E4 to E3. The minor alkaloid cathedulin K12, C54H62N2O23, has the structure (18), similar to E3 but with the cathate span reductively cleaved : this suggests a biosynthetic connection.

Extractives of Catha edulis(Khat): occurrence of celastraceaeous alkaloids having mono- and bis-macrolide bridges

Six purified alkaloids have been isolated from C. edulis: four have mol. wts > 1100, two (cathedulin-5 and -6) being mono-macrolide-bridged and two (cathedulin-3 and -4) bis-macrolide-bridged derivatives of euonyminol.

Structures of cathedulin-2 and cathedulin-8, new sesquiterpene alkaloids from Catha edulis

The structures of cathedulin-2 and -8, alkaloids from C. edulis, are shown to be (1) and (2) respectively.

Comparison of the structure property relationships in LB films of zwitterionic TCNQ adducts

Substitution reactions of TCNQ (7,7,8,8-tetracyanoquinodimethane) with suitable quinolinium and picolinium electron donor moieties yielded an extensive analogous series of α-bridged quinolinium and picolinium adducts R(2)Q3CNQ and R(2)P3CNQ respectively of which the long chain (Z)-{β-[N-(1-hexadecyl)quinolinium-2-yl]-α-cyano-4-styryl}-dicyanomethanide (C16H33(2)Q3CNQ) is a typical example. These zwitterionic D–π–A materials (where D and A are electron donor and acceptor respectively) exhibit properties such as solvatochromism, molecular rectification and second harmonic generation and were compared and contrasted to the existing γ-bridged adducts. The behaviour of the materials on the water subphase and their resultant Langmuir–Blodgett (LB) film fabrication were studied. The abrupt change in molecular orientation in LB films of the γ-bridged adducts occurring at R = C15H31 and above was not seen in the more flatly orientated α-bridged adducts. Further characterisation of the LB films was performed using reflectance–absorption infra-red spectroscopy (RAIRS) and surface plasmon resonance (SPR). The crystal structure of the long chain adduct, C10H21(2)Q3CNQ, is also reported.

Convenient syntheses of bifunctional C12-acyclic compounds from cyclododecanone

The conversion of cyclododecanone by convenient, non-hazardous, and high-yielding reactions into a set of useful C12-bifunctional intermediates is described. Baeyer–Villiger oxidation and hydrolysis give a hydroxy acid, successively converted into the bromo acid, bromo alcohol, crude bromo aldehyde, pure bromo aldehyde ethylene acetal, and pure bromo aldehyde. Preferred reagents for the transformation CO2H → CHO are borane–dimethyl sulphide followed by dimethyl sulphoxide–oxalyl dichloride–triethylamine.