Raphael M. Munavu

The preparation of 5-hydroxymethyl-2-furaldehyde (HMF) from d-fructose in the presence of DMSO

Abstract 5-Hydroxymethyl-2-furaldehyde (HMF, 1) was produced in 92% yield when d -fructose was dehydrated using dimethylsulphoxide (DMSO) at 150°C for 2 h. The optimum conversion occurred at a d -Fructose: DMSO molar ratioof 8.0. In addition to HMF, small quantities (⪷ 1%) of oxobis (5-methyl-2-furaldehyde), 4, were also obtained from the reaction. The amount of 4 was substantially increased (⪷ 30%) when the reaction was carried out in toluene as the solvent with borontrifluoride etherate as the catalyst.

Essential Oils of Lippia Species in Kenya. IV: Maize Weevil (Sitophilus Zeamais) Repellancy and Larvicidal Activity

AbstractThe repellancy of essential oils of eight Lippia species on maize weevils was compared with NN-diethyltoluamide (DEET). The larvicidal activity of these essential oils was also examined. As a repellant, the essential oil of L. ukambensis (chemotype camphor) was the most active. Other promising repellants were the essential oils of L. javanica, L. dauensis, L. somalensis and L. grandifolia. The essential oil of L. wilmsii was the most active as a larvicide. Individual hydrocarbon monoterpene constituents were generally more active than the oxygenated constituents of the essential oils.

The pyrrolizidine alkaloids of Senecio syringifolius and S. hadiensis from Kenya

Abstract Angularine, rosmarinine and 12- O -acetylrosmarine, together with their N -oxides were isolated from epigeal parts of S. syringifolius , while

Essential Oils of Two Lippia ukambensis Vatke Chemotypes and Lippia somalensis Vatke in Kenya

ABSTRACT The chemical composition of the essential oils of 41 samples of Lippia ukambensis Vatke were examined by GC/MS. Two chemotypes were identified on the basis of the camphor and 1, 8-cineole. The camphor chemotype of L. ukambensis contained camphor (37.3%) with only traces of 1, 8-cineole, while the other chemotype contained 1, 8-cineole (23.7%) and only 1.1% camphor. Of the twelve components which were present in both chemotypes, only eight were quantitatively significantly different. The major compound in the oil of L. somalensis was 1, 8-cineole (31.9%). By using fifteen components of L. somalensis oil, its similarities and differences with those of the two Lippia chemotypes were compared.

Plucking standard effects and the distribution of fatty acids in the tea (Camellia sinensis (L.)) leaves

Abstract The order of occurrence of fatty acids (FA) in the leaves and stem of tea shoots is linolenic acid > linoleic acid > palmitic acid > stearic acid > oleic acid > palmitoleic acid, irrespective of the plucking standard or portion of the shoot. The stem had the least FA levels. Linolenic acid dominated the FA and increased with maturity of the leaf and coarser plucking standard. Similarly, total FA, total unsaturated FA and linolenic plus linoleic acids increased with coarse plucking standard and maturity of the leaf. This explains quality deterioration due to the higher amount of the group I volatile flavour compounds arising from the coarse plucking standard.

The principal alkaloid of Senecio schweinfurthii

Air-dried epigeal parts of Senecio schweinfurthii, collected from two sites in Kenya, yielded 7β-hydroxy-1-methylene-8α-pyrrolizidine N-oxide, as the predominant alkaloid.

2-Thiazolines in organic synthesis. Formation of. beta.-hydroxy aldehydes with protected hydroxy groups. Synthesis of homoallylic alcohols

Die aus 2-Methylthiazolin (I) mit Butyllithium erhaltene Organometallverbindung reagiert mit Oxo-Verbindungen (II) zu den Carbinolen (III), die nach Al-Amalgamreduktion zu (IV) mit Hg(II)-Salzen zu Hydroxy-aldehyden (V) gespalten werden.

Fatty acid composition of seed kernel oil of Calodendrum capense (L. f.) Thunb.

Seed kernels ofCalodendrum capense (L.f.) Thunb. yielded 60% of a light yellow oil which had the following fatty acid composition: 23.8% palmitic, 4.5% stearic, 33.7% oleic, 35.6% linoleic, 1.4% linolenic and 1.0% arachidic. Myristic and behenic acids were present in trace amounts, and the kernel cake contained 37.6% crude protein.

Changes in fatty acid levels of young shoots of tea (Camellia sinensis L.) due to nitrogenous fertilizers.

Abstract The unsaturated fatty acids (FA), linolenic acid (C18:3) and linoleic acid (C18:2), responsible for the production of undesirable volatile flavour compounds in black tea, dominate FA composition of young shoots of clonal tea. These FA levels increase with increase in nitrogeneous fertilizer rates whether NPKS 25:5:5:5 or NPK 20:10:10 fertilizer is used. Results explain the general flavour quality deterioration with increase in nitrogenous fertilizer rates.

The conversion of 2-furaldehyde into some potentially useful bifunctional derivatives

2-Fluraldehyde was converted into 2-(5-R-2-furyl)-1, 3-dioxanes; 5-R-2-cyanofurans where R = H, Br, I or NO2; bis(5-bromo-2-furyl-1,2-R diimine where R = ethyl or butyl; and 5-hydroxymethyl-2-furaldehyde. Furfuryl alcohol, obtained from 2-furaldehyde by the Cannizaro reaction, and 5-hydroxymethyl-2-furaldehyde were reacted with hydrogen sulphide to give 2,2′-difurfuryl thioether in 5% yield and thiobis (5-methyl-2-furaldehyde) in 6% yield, respectively. Furfuryl alcohol reacted with 5-hydroxymethyl-2-furaldehyde to yield 5-formyl-2,2′-difurfuryl ether in 6% yield. The dioxanes were found to decompose when stored at room temperature for more than six months, while the other compounds were relatively stable when stored for the same period of time.