Browsing by Author "Kishimba, Michael Andrew"

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    Chemical studies on some diospyros species
    (University of Dar es Salaam, 1985) Kishimba, Michael Andrew
    The isolation and subsequent identification of naphthoquinones and triterpenoids from six Diospyros species collected in Tanzania is discussed. In the present investigation, diosindigo A has been either isolated or detected in the root and stem barks of all the species studied. Diosindigo B was isolated from the root bark of D.usambarensis and the root bark of D. zombensis, while 7 -methyl jug lone was found in the stem barks of D. usambarensis, D. zombensis , D. verrucosa and D. squarrosa. Diosquinone, isodiospyrin , betulin and betulinic acid were isolated from the root and stem barks of D. verrucosa. The barks of D. consolatae and D. cornii yielded betulinic acid together with α-amyrin in the latter and lupeol in the former. Mamegakinone was found in the stern and root barks of D. usambarensis and D. zombensis, with bis-isodiospyrin in the former species. Two violet quinones were also detected. One was detected in the rootbarks of D. usambarensis and D. zombensis while the other was detected in the stem bark of the latter. The potential of diosindigo A as a biological marker for genus Diospyros is also discussed.
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    Synthesis of Carba-strigol analogues
    (University of Dar es Salaam, 1991) Kishimba, Michael Andrew
    This thesis describes the synthesis of novel strigol analogues in which the enol-ether oxygen in th analogues has been replaced by a methylene group. These compounds are called carba-strig analogues. The GR 5 carba-strigol analogue { 3-Methyl-5[(-3-ethanylidene-4,5-dihydro-: oxo-2(3H)furanone)-1')-2(SH)furanone} was prepared by a Wittig reaction of th a-triphenylphosphorane of y-butyrolactone and 5-[(1-oxoethyl)-2'-]-3-methyl-2(SH)furanone. The othe three carba-strigol analogues, E-3-Methyl-5{[-3-ethanylidene)-1')-3,3a,6,6a-tetrahydro-2H-cyclc penta[b]furan-2-one}-2(SH)furanone, E-3-Methyl-5{[(-3-ethanylidene)-1']-3,3a,4,8b-tetrahydrc -4H-indeno[1,2-b]-furan-2-one }-2(3H)furanone and E-3-Methyl-5{ [(-3-ethanylidene)-1')-3,3,3a,4,6a -tetrahydro-4H-cyclopenta[b)furan-2-one }-2(3H)furalnone were prepared by coupling the respectiv parent lactones to 5-[(1-oxoethyl)-2-)-3-methyl-2(SH)furanone using LDA an (methoxythiocarbonyl)disulphide. An alternative approach to the synthesis of E-3-Methyl-5 { [-3-ethanyl idene)-1']-3,3a,6,6a-tetrahydro-2H-cyclopenta[b)furan-2-one}-2(SH)furanone, and E-3-Methyl -5{[(-3-ethanylidene)-1')-3,3a,4,8b-tetrahydro-4H-indeno[1,2-b]-furan-2-one}-2(3H)furanone using the Wittig-Homer method is also described. The facile synthesis of 5-[(1-oxoethyl)-2-] and 5-brom substituted 3-methyl-2(SH)furanones as well as model compounds for the carba-strigol analogues of GF 7, GR 28 and GR 24 {E-3-Benzylidene-3,3a,6,6a-tetrahydro-6H-cyclopenta[b)-furan-2-one, E-3 Benzylidene-3,3a,4,6a-tetrahydro-4H-cyclopenta[b)-furan-2-one and E-3-Undecylidene-3,3a,4,8b~ -tetrahydro-4H-indeno[1,2-b]-furan-2-one}, is also reported.