Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
Search results
43 records were found.
A novel aromatised 8(14)-secohopanoid 1 (C31H42) possessing a fluorene moiety, formed from derivatives of bacteriohopanepolyols by cyclisation, aromatisation, ring opening and side-chain cleavage reactions during sediment diagenesis, has been isolated from a 150 Ma old marine sedimentary rock and identified by 1H and 13C NMR spectroscopy and mass spectrometry.
A novel diaryl isoprenoid 1 with an additional aromatic ring (C30H38), formed from the carotenoid -carotene by cyclisation, aromatisation and expulsion reactions during sediment diagenesis, has been isolated from a 50 Ma old lacustrine sedimentary rock and identified by 1H and 13C NMR spectroscopy and mass spectrometry.
C21 and C22 highly branched isoprenoid (HBI) alkanes occurring in high relative abundance in lagoonal sediments of
Abu Dhabi have been unambiguously identified as 2,6,10-trimethyl-7-(3-methylpentyl)dodecane and 3,7,11-trimethyl-6-
(3-methylpentyl)tridecane, respectively, using NMR spectroscopy. A second C21 HBI isomer is tentatively identified as
3,7,11-trimethyl-6-(3-methylbutyl)tridecane, on the basis of comparison of its mass spectral fragmentation with those of
fully identified HBIs. The structures of these three components are formed by extension of the "parent" C20 HBI
alkane, first identified in Rozel Point Oil by Yon et al. [Yon, D.A., Maxwell, J.R., Ryback G., 1982. 2,6,10-trimethyl-
7-(3-methylbutyl)dodecane, a novel sedimentary biological marker. Tetrahedron Letters 23, 2143–2146], by
one or two carbon atom(s), respectively,...
Steryl alkyl ethers have been reported to occur in immature marine sediments up to Cretaceous age. Here, we report
their unambiguous structural identification in Holocene sediments from the Arabian Sea, Pleistocene sediments from
the southeast Atlantic and a Miocene sediment from the Monterey formation through chemical degradation experiments
and synthesis. We show that the main steryl alkyl ethers in sediments from the southeast Atlantic are cholest-
5-enyl 3β-(2-dodecanyl) ether and cholest-5-enyl 3β-(3-dodecanyl) ether together with their 24-methyl and 24-ethyl
pseudo-homologues. Steryl alkyl ethers in sediments from the Arabian Sea are dominated by cholest-5-enyl 3β-(5-decanyl)
ether and cholest-5-enyl 3β-(4-decanyl) ether together with their 24-methyl and 24-ethyl pseudo-homologues. The
structures suggest that these compounds are ...
A new coumarin, 4-methoxy-5-hydroxymethylcoumarin was isolated from the root bark of Ekebergia benguelensis, together with the polyhydroxysqualenes, 2,22,23-tetrahydroxy-2,6,10,15,19,23-hexamethyl-6,10,14,18-tetracosatetraene and 2-hydroxymethyl-2,3,22,23-tetrahydroxyl-6,10,15,19,23-pentamethyl 1-6,10,14,18-tetracosatetraene, besides a mixture of 3α-hydroxy-12-oleanen-28-oic and 3-oxo-12-oleanen-28-oic acids. Structural determination was achieved by spectroscopic analyses.
The basic structure and stereochemistry of the characteristic glycerol dibiphytanyl glycerol tetraether (GDGT) membrane lipid of cosmopolitan pelagic crenarchaeota has been identified by high field two-dimensional (2D)-NMR techniques. It contains one cyclohexane and four cyclopentane rings formed by internal cyclisation of the biphytanyl chains. Its structure is similar to that of GDGTs biosynthesized by (hyper)thermophilic crenarchaeota apart from the cyclohexane ring. These findings are consistent with the close phylogenetic relationship of (hyper)thermophilic and pelagic crenarchaeota based 16S rRNA. The latter group inherited the biosynthetic capabilities for a membrane composed of cyclopentane ring-containing GDGTs from the (hyper)thermophilic crenarchaeota. However, to cope with the much lower temperature of the ocean, a small bu...
All trans 2,6,10,15,19-pentamethylicosa-2,6,14,18-tetraene 1 has been isolated from the methanogenic archaeon Methanosarcina mazei and identified by 1H and 13C NMR spectroscopy and mass spectrometry
