Source: http://oneorganichemistoneday.blogspot.com/2015_01_19_archive.html
Timestamp: 2019-04-21 12:08:55+00:00

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Doctor of Philosophy (PhD) in Analytical/Environmental Chemistry.
Master of Science (MSc) In Chemistry.
1979–1982 University of Nairobi, Master of Science (MSc) in Chemistry.
1970-1973 Ngandu Girls High School, Kenya Certificate of Secondary Education.
1976 Teaching (Mathematic and Chemistry), Gatanga Girls secondary School.
Professor Lydia Wanjiru Njenga Dean School of Physical Sciences (Pictured) was appointed the Director, Board of Postgraduate Studies, University of Nairobi for a term of three years with effect from January 2, 2015.
The appointment was contained in a letter dated January 2, 2015 and signed by the Vice Chancellor, Professor George A. O. Magoha. Prof. Njenga replaces Prof. Eunice W. Mutitu whose second term as director of the Board of Postgraduate Studies expired on January 2, 2015 after serving for six years.
A holder of a Doctor of Philosophy in Analytical/ Environmental Chemistry, Prof. Njenga was tyhe Dean School of Physical Sciences, is an associate professor in the department of Chemistry having risen through academic levels since 1983 when she first joined the department as a Tutorial Fellow. Prof. Njenga brings along with her a wealth of academic and administrative experience, having served as Dean, School of Physical Sciences. She has also served in several college and faculty committees and was the advisor to the Nairobi University Chemical Club, among other responsibilities.
Prof. Njenga has been Dean School of Physical Sciences For Four years,an external examiner in several local and international universities and has supervised two PhD candidates, several Masters and undergraduate students to completion. Her research interest is in Fluoride analysis in water, foods, plants and soils and coordination Chemistry. She has attended 40 local and international conferences and workshops and presented 14 papers and six reports. Prof. Njenga is widely published with 16 articles in Refereed Journals and has authored two Open and distance learning Modules entitled, “Coordination Chemistry” and “Transition Elements (d and f block elements) and Organometallic Chemistry”.
Prof. Njenga is a member of Kenya Chemical Society, Women in Science and Engineers, Women in Chemistry, Kenya DAAD Association and East and Southern Africa Environmental Chemistry. She engages in several community service initiatives.
The Fountain of Knowledge at the University of Nairobi.
African Journal of Physical Science 6 (2) (2005) 57-66.
Comparison of Direct, Oven Diffusion and Hexamethyldisiloxane Diffusion method”.
sources of fluoride around Lake Elementaita”. Fluoride 30 (1997) 19-25.
Extracting Medias”. International Journal of BioChemiPhysics, 3, (1994) 18 – 22.
11. L. W. Njenga and D. N. Kariuki: “Accumulation of fluoride in plants and vegetables”.
International Journal of BioChemiPhysics, 3, (1994) 23 - 25.
BioChemiPhysics, 3, (1994) 75 - 76.
selective electrode”. Ph D. Thesis (1989), University of Nairobi.
15. D. N. Kariuki, H. M. Thairu, L. W. Njenga: (1984) “Dietary sources of fluoride in Kenya”.
Paper published in the proceedings of the workshop on “Fluorosis Research Strategies.
Published in African Medical and Research Foundation 36  32 - 6.
Reviewed by Prof Shem O. Wandiga (Professor of Chemistry) and edited by Mr J. O.
Everyone can afford an avocado, and many pick one up and have it cut into quarters, for immediate consumption as they walk on. Nairobi street food is good!
1. PILLI, R. A. ; Ângelo de Fátima ; Luciana Konecny Kohn ; CARVALHO, J. E. . Cytotoxic Activity of (S)-goniothalamin and Analogues Against Human Cancer Cells. Bioorganic & Medicinal Chemistry, Estados Unidos, v. 14, p. 622-631, 2006.
2. PILLI, R. A. ; Andrea Leal de Sousa . A concise route to the azaspirodecane moiety of halichlorine and structurally related alkaloids. Organic Letters, Washington, DC, v. 7, p. 1617-1619, 2005.
3. PILLI, R. A. ; MALDANER, A. O. ; CORREA JR., I. R. ; ROSSO, G. B. . Total Synthesis and Structural Elucidation of Natural Products: (-)-Delactonmycin, (+)-Plumerinine and (-)-Parvistemoamide . Pure and Applied Chemistry, Grã-Bretanha, v. 77, p. 1153-1160, 2005.
4. PILLI, R. A. ; SANTOS, L. S. ; RAWAL, V. . Enantioselective Total Syntheses of (+)-Arborescidine A, (-)-Arborescidine B, and (-)-Arborescidine C. Journal of Organic Chemistry, Washington, DC, v. 69, p. 1283-1288, 2004.
5. PILLI, R. A. ; CORREA JR., I. R. . Total Synthesis and Structural Elucidation of (-)-Delactonmycin. Angewandte Chemie, Alemanha, v. 42, p. 3017-3020, 2003.
To a solution of oxalyl chloride (0.013 mL, 0.15 mmol) in CH2Cl2 (1.0 mL) at -78 °C was added dimethyl sulfoxide (0.020 mL, 0.31 mmol) dropwise. The solution was stirred 10 min at -78 °C and a solution of a mixture of 11 and 12 (0.023 g, 0.089 mmol) in CH2Cl2 (1.0 mL) was added. The mixture was stirred 1.5 h at -78 °C, and treated with triethylamine (0.06 mL, 0.46 mmol). After warming to room temperature, the reaction was quenched with water, the layers were separated and the aqueous layer was extracted with CH2Cl2 (3 x 2 mL). The combined organic phases were washed with brine (4 mL), dried over MgSO4 and concentrated under reduced pressure. The residue (0.019 g) was dissolved in THF (1 mL) at room temperature and treated with 1.0 M solution of TBAF (0.1 mL, 0.1 mmol) in THF. The mixture was stirred 1 day at room temperature, diluted with Et2O (10 mL) and treated with aq. NH4Cl (3 mL). The layers were separated and the aqueous layer was extracted with Et2O (3 x 4 mL). The combined organic layers were dried over MgSO4 and concentrated. Silica gel chromatography (30% AcOEt in hexanes, v/v) afforded (+)-1 (0.0074 g, 0.052 mmol) in 60% yield, as a colorless oil.
1H-NMR (CDCl3, 300 MHz): d 0.96 (t, 3H, J = 7 Hz); 1.06 (t, 3H, J = 7 Hz); 1.14 (d, 3H, J = 7 Hz); 1.37 (ddq, 1H, J = 15, 7 and 3 Hz); 1.51 (ddq, 1H, J = 15, 8 and 7 Hz); 2.42-2.70 (m, 3H); 2.86 (br s, 1H); 3.83 (ddd, 1H, J = 8, 5 and 3 Hz).
13C-NMR (CDCl3, 75.5 MHz): d 7.6; 9.9; 10.4; 26.8; 35.1; 49.3; 72.6; 216.8.
IR (film): 3453; 1701; 1460 cm-1. [a]D +24.8 (c1.24, Et2O). lit.2: [a]D +27.0 (c1.24, Et2O).
The Asymmetric Synthesis of (+)-Sitophilure, the Natural Form of the Aggregation Pheromone of Sitophilus oryzae L. and Sitophilus zeamais M.
In 1984, Burkholder and coworkers isolated the male-produced aggregation pheromone of the pests rice weevil (Sitophilus oryzae L.) and maize weevil (Sitophilus zeamais M.), which is named Sitophilure. This biologically-active compound was first identified as (4R,5S)-5-hydroxy-4-methyl-3-heptanone, from the extracts of thousands of insects. All four stereoisomers of this pheromone were synthesized and it was proved that the active form of this compound is the (4S,5R) enantiomer. Since then, several total syntheses of racemic, or other stereoisomers and the natural form of this pheromone have been published.
Serious economic losses of stored cereal grains (maize, rice and grain) are mainly caused by three weevils of the genus Sitophilus(Sitophilus zeamais, Sitophilus oryzae, Sitophilus granarius respectively) throughout the world. Early detection of infestations is critical in order to avoid further damage to the grains and the subsequent economic losses. Traps that contain very small amounts of synthetic (+)-sitophilure have been shown to be very effective in the early detection of all three species of weevils,however a simple scalable and economic method for the synthesis of this weevil attractant pheromone is still lacking.[9-12] As a result, all of the commercially available traps for the early detection of these weevils are food-based.
The absolute stereochemistry of the enantiomers B and D (Scheme 3) was found to be (4S,5R) and (4S,5S) respectively, taking into account that the relative stereochemistry of the product D is anti and of the product B syn.
As we can see in Scheme 3, the product from the reduction of 4-methyl-3,5-heptanedione with KRED-A1C has the same stereochemistry with that of the natural pheromone (+)-Sitophilure. These results clearly indicate that ketoreductases KRED-A1B, KRED-A1C and KRED-A1D showed unusual anti-Prelog selectivity, concerning reduction of the 5-keto group and successfully produced the keto alcohol with the desired stereochemistry 4S,5R. So the natural product can be produced easily from the corresponding diketone.
In large scale, the reaction is completed in 24 hours, producing the pheromone with chemical yield 85%, de 96%, ee >99%, and chemical purity >99%, utilizing catalytic amounts of the NADPH cofactor (0.81% relative to the substrate), which was recycled in situ using Glucose Dehydrogenase (GDH). The corresponding 4-methyl-3,5-heptanedione can be readily produced from the commercially available 3,5-heptanedione (Scheme 4).
A phosphate-buffered solution (16 mL, pH 6.5, 200 mM) containing 84 mM (1.35 mmol, 192 mg) of 4-methyl-3,5-heptanedione, NaCl (200 mM, 200 mg), glucose (130 mM, 375 mg), NADPH (0.69 mM, 0.011 mmol, 10 mg), glucose dehydrogenase (10 mg) and KRED-A1C (10 mg) was stirred at 25° C. for 24 hours, until GC analysis of crude extracts showed complete reaction. Periodically the pH was readjusted to 6.5 with NaOH (2 M). The product was isolated by extracting the crude reaction mixture with EtOAc (15 mL×2). The combined organic layers were then extracted with saturated NaCl solution, dried over MgSO4 and evaporated to dryness. Pure (4S,5R)-5-hydroxy-4-methyl-3-heptanone (165 mg) was obtained in 85% yield. 1H NMR (CDCl3 500 MHz, δ ppm):1H NMR (CDCl3 500 MHz, δ ppm): 3.77-3.85 (m, 1H), 2.72 (s, OH), 2.41-2.64 (m, 3H), 1.32-1.58 (m, 2H), 1.12 (d, J=7.1 Hz, 3H), 1.05 (t, J=7.3 Hz, 3H), 0.95 (t, J=7.4 Hz, 3H). 13C NMR (CDCl3 300 MHz, δ ppm): 216.7, 72.6, 49.3, 35.1, 26.9, 10.4, 9.9, 7.6.
Determination of the Enantiomeric Purity of (4S,5R)-5-hydroxy-4-methyl-3-heptanone: GC (column: 30 m×0.25 mm×0.25 μm chiral capillary column, 20% permethylated cyclodextrin 65° C. for 100 min, rate: 1° C./min, final temp.: 100° C.; carrier gas: N2, press 70 kPa). tR=100.0 min [98%, (4S,5R)-5-hydroxy-4-methyl-3-heptanone], tR=105.1 min [2%, (4R,5R)-5-hydroxy-4-methyl-3-heptanone]. The enantiomeric purity was estimated to be >99% and the diastereomeric purity 96%.
Administração e Biblioteca do Instituto de Química da UNICAMP, Campinas.
Images from top, left to right: Metropolitan Cathedral, an avenue in Campinas's downtown,an old railway station, Mogiana Palace, a monument to the heroes of Constitutionalist Revolution (in Saudade Cemetery), a bus terminus, Central area of Campinas as seen fromTorre do Castelo, a belvedere.

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