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Synthesis, conformation analysis, and characterization of physiologically important flavonoids and isoflavonoids
No full textThis work contains two parts of study: Synthesis of a series of homoisoflavonoid analogues in
order to investigate a difference between 6- and 8- homoisoflavanone which isolated from Scilla
Natalensis and Part II contains conformational analysis of C-ring substituted flavans and
analogues.
While the novel homoisoflavanone isolated from Scilla natalensis as the peracetate has
unambiguously been proven by synthesis to have the 5,7,4’-triacetoxy-8-methoxy structure
during this investigation. The control of the substituents (protecting groups) is determined the Aring
of a homoisoflavanone which has also been pointed out that great care should be taken in the
assignment of the structures of these compound by comparison of proton chemical shifts. This is
especially true when a single methoxy group is situated on a trioxygenated A-ring as there might
not be an nOe association between the methyl protons and any aromatic hydrogen. The situation
may further be aggravated by the fact that natural products may be isolated as derivatives, like
peracetates, of the naturally occurring free phenolic analogues due to separation difficulties.
Although only two of the possible 6 A-ring trioxygenated homoisoflavanones have been
synthesised e.g. 5,7,4’-trihydroxy-6-methoxyhomoisoflavanone and 5,7,4’-trihydroxy-8-
methoxyhomoisoflavanone, it is envisaged that the remaining four compounds will also be
prepared so the 1H and 13C NMR data of all these compounds both as free phenols and
peracetates can be reported. This will be a valuable tool to assist researchers during the isolation
and structure elucidation of this class of natural product during future phytochemical
investigations.
In an effort to divulge the effect of the individual stereocenters form each other, and thus the
combined effet obtained by ECD, it was decided to investigate the chromophore based method of
VCD as measurement of absolute configuration at the different stereogenic centres. If a
correlation between the IR absorption band(s) at certain wave numbers and a specific
chromophore in a molecule could be established, it should, in principle, be possible to define the
absolute comfiguration at that point in the molecule by VCD. In order to find a possible
relationship between chromophores and IR absorption bands in flavonoids and related molecules, a molecular modelling study to determine the preferred conformation of the heterocyclic ring of
these compounds as well as establish a possible correlation between the chromophore present in
the molecule and IR band(s) was embarked upon. In this regard, the preferred conformation(s) of
the series of heterocyclic molecules with increasing order of complexity, i.e. no substituent to
three heterocyclic substituents, were determined and correlated with the respective modelled IR
frequencies as well as the experimental absorption bands in the IR spectrum.
In this study a complete conformational surface of oxane, chromane, flavan, flavan-3-ols, 4-
arylflavan and 4-arylflavan-3-ols is presented to give the global and local minima which reulted
in finding the most stable conformations. However, the most stable conformations for these
compounds are the chair, 2,5-twisted boat and 1,4-twisted boat (oxane); half chair (chromane);
[(2R)-equatorial and (2S)-equatorial (flavan)]; [(2S)-equatorial, (3S)-axial and (2S)-equatorial,
(3R)-equatorial (flavan-3-ol)]; [(2S)-equatorial, (4R)-axial and (2S)-equatorial, (4S)-equatorial
(4-arylflavan)] and {[(2S)-axial, (3S)-equatorial, (4R)-axial], [(2S)-axial, (3S)-equatorial,
(4S)-equatorial], [(2S)-equatorial, (3R)-equatorial, (4R)-equatorial] and [(2S)-equatorial,
(3R)-equatorial, (4S)-axial] (4-arylflavan-3-ols)}. The assignment of IR absorption from
theoretical spectra is presented and the excellent match between theoretical and experimental IR
analysis is achieved. It’s evidently concluded that the method of using TDDFT calculations
together with infrared spectroscopy to determine the most stable or preferred conformation was
achieved for flavonoid compounds. The determining of absolute configuration at a chiral centre
in selected flavonoid compounds and understanding of its IR spectra is currently under
investigation with the same approach.
The calculated VCD spectrums of the highest populated conformations are presented e.g. [(2R)-
equatorial (flavan)]; [(2S)-equatorial, (3S)-axial and (2S)-equatorial, (3R)-equatorial (flavan-3-
ol)]; [(2S)-equatorial, (4R)-axial and (2S)-equatorial, (4S)-equatorial (4-arylflavan)] and {[(2S)-
axial, (3S)-equatorial, (4R)-axial], [(2S)-axial, (3S)-equatorial, (4S)-equatorial], [(2S)-
equatorial, (3R)-equatorial, (4R)-equatorial] and [(2S)-equatorial, (3R)-equatorial, (4S)-axial]
(4-arylflavan-3-ols)} were also achieved successfully.SASOLUniversity of the Free Stat
SWART, Charles Robberts Inventory of documents
No full textCOVERAGE 1852-1982; 393 Files; 13,80 Metres.
AUDIO CASSETTES IN ARCA COLLECTION = 13Private papers of C.R. Swart, Organising Secretary National Party Free State [1919-1928], MP Ladybrand [1923-1938], Winburg [1941-1958], Leader NP in the Free State [1940-1959], Leader of the House of Assembly [1954-1959], Minister of Justice [1948-1959], Education, Arts and Science [1949-1950], Governor-General [1960-1961], First State President of the RSA [1961-1967]
VILJOEN, Johannes Hendrikus Inventory of documents
No full textCOVERAGE 1913-1958; 35 Files; 0,33 Metres.Private papers of J.H. Viljoen, National Party MP Hoopstad [1933-1934], United Party MP Hoopstad [1934-1941], Afrikaner Party [1941-1943], National Party MP Vryburg [1948-1957], Minister of Mines [1950-1953], Education Arts and Science [1950-1957], Social Welfare [1953-1954], Forestry [1954-1956] Health [1956-1957]
HELPMEKAARVERENIGING OF THE CAPE PROVINCE Inventory of documents
No full textCOVERAGE 1915-1917; 1 File; 0.11 metrePapers of the Helpmekaarvereniging of the Cape Province. The "Help-Each-Other-Society" was founded in June 1916 in Cape Town to assist rebels of the 1914 Rebellion financially
TAYLOR, Y. Inventory of documents
No full text1938-1961; 3 Files; 0.44 metrePrivate papers of Y. Taylor, teacher [1945-1949]; clerk attorney's office [1950-1962]; clerk CSIR Library [1962-1966]
JERLING, Jacobus Daniël Inventory of documents
No full textCOVERAGE 1914-1967; 37 Files; 0,78 Metres.Private paper of J.D. Jerling, member of the Ossewa-Brandwag, with the rank of Assistant-Commandant-General
HEUNIS, Jan Christiaan [Chris] Inventory of documents
No full textCOVERAGE 1965-1990; 834 Files; 38,10 Metres.
AUDIO CASSETTES IN ARCA COLLECTION = 6Private papers of J.C. Heunis, National Party MP False Bay [1970-1974], Helderberg [1974-1989], Deputy Minister of Finance [1972-1974], Economic Affairs [1972-1974], Minister of Indian Affairs [1974-1975], Tourism [1974-1975], Economic Affairs [1975-1979], Planning and the Environment [1978-1979], Environmental Planning and Energy [1979], Transport Affairs [1979-1980], Internal Affairs [1980-1982], Constitutional Development [1982], Constitutional Development and Planning [1982-1989]
The 17th century Johannes Hoornbeeck's view on mission, ecumenism and historical theology and its current relevance
No full textIn this second article (cf. Hofmeyr 2016), like the previous one, I would like to introduce Johannes Hoornbeeck and the Further Reformation, besides other goals, to the Anglo-Saxon world. This article focuses primarily on the 17th-century theologian Johannes Hoornbeeck and some of his views within the context of the Further Reformation. I address the issue related to an analysis of Hoornbeeck’s contributions as a missiologist, a theologian with a clear ecumenical and irenical orientation, and a historical theologian. In my opinion, he can be regarded as the second most prominent theologian, besides Gisbertus Voetius. In some respects, Hoornbeeck even surpasses him. This critical overview also focuses on the Further Reformation as an ecclesiastical and theological development.Publisher's versio