RATES OF SOLVOLYSIS OF SOME DEUTERATED 2-PHENYLETHYL p-TOLUENESULFONATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saunders, W.H. Jr.; Asperger, S.; Edison, D.H.

1958-05-20

Rates of solvolysis of 2-phenylethyl (Ia), b 2/ (Ic) p-toluenesulfonates were determined in formic and in acetic acid. In formolysis Ia and Ic react at the same rate, but Ia reacts 17 plus or minus 2% faster than Ib. In acetolysis small effects are observed with both deuterated com. pounds: Ia is 3 plus or minus 1% faster than Ib and 4 plus or minus 3% faster than Ic. The formates and acetates produced in the solvolyses were converted to the corresponding 2phenylethanols II. Comparison of the infrared spectra of the products with those of synthetic mixture of IIb andmore » IIc revealed that ca. 45% phenyl migration had occurred in the formolysis and ca. 10% phenyl migration in acetolysis. These results suggest that phenyl participation predominates in formolysis, but is unimportant in acetolysis. The nature of the transition state in phenyl- participation reactions and the factors contributing to secondary deuterium isotope effects are discussed. (auth)« less

The impact of oxidation on spore and pollen chemistry: an experimental study

NASA Astrophysics Data System (ADS)

Jardine, Phillip; Fraser, Wesley; Lomax, Barry; Gosling, William

2016-04-01

Sporomorphs (pollen and spores) form a major component of the land plant fossil record. Sporomorphs have an outer wall composed of sporopollenin, a highly durable biopolymer, the chemistry of which contains both a signature of ambient ultraviolet-B flux and taxonomic information. Despite the high preservation potential of sporopollenin in the geological record, it is currently unknown how sensitive its chemical signature is to standard palynological processing techniques. Oxidation in particular is known to cause physical degradation to sporomorphs, and it is expected that this should have a concordant impact on sporopollenin chemistry. Here, we test this by experimentally oxidizing Lycopodium (clubmoss) spores using two common oxidation techniques: acetolysis and nitric acid. We also carry out acetolysis on eight angiosperm (flowering plant) taxa to test the generality of our results. Using Fourier Transform infrared (FTIR) spectroscopy, we find that acetolysis removes labile, non-fossilizable components of sporomorphs, but has a limited impact upon the chemistry of sporopollenin under normal processing durations. Nitric acid is more aggressive and does break down sporopollenin and reorganize its chemical structure, but when limited to short treatments (i.e. ≤10 min) at room temperature sporomorphs still contain most of the original chemical signal. These findings suggest that when used carefully oxidation does not adversely affect sporopollenin chemistry, and that palaeoclimatic and taxonomic signatures contained within the sporomorph wall are recoverable from standard palynological preparations.

Resistant tissues of modern marchantioid liverworts resemble enigmatic Early Paleozoic microfossils

PubMed Central

Graham, Linda E.; Wilcox, Lee W.; Cook, Martha E.; Gensel, Patricia G.

2004-01-01

Absence of a substantial pretracheophyte fossil record for bryophytes (otherwise predicted by molecular systematics) poses a major problem in our understanding of earliest land-plant structure. In contrast, there exist enigmatic Cambrian–Devonian microfossils (aggregations of tubes or sheets of cells or possibly a combination of both) controversially interpreted as an extinct group of early land plants known as nematophytes. We used an innovative approach to explore these issues: comparison of tube and cell-sheet microfossils with experimentally degraded modern liverworts as analogues of ancient early land plants. Lower epidermal surface tissues, including rhizoids, of Marchantia polymorpha and Conocephalum conicum were resistant to breakdown after rotting for extended periods or high-temperature acid treatment (acetolysis), suggesting fossilization potential. Cell-sheet and rhizoid remains occurred separately or together depending on the degree of body degradation. Rhizoid break-off at the lower epidermal surface left rimmed pores at the centers of cell rosettes; these were similar in structure, diameter, and distribution to pores characterizing nematophyte cell-sheet microfossils known as Cosmochlaina. The range of Marchantia rhizoid diameters overlapped that of Cosmochlaina pores. Approximately 14% of dry biomass of Marchantia vegetative thalli and 40% of gametangiophores was resistant to acetolysis. Pre- and posttreatment cell-wall autofluorescence suggested the presence of phenolic compounds that likely protect lower epidermal tissues from soil microbe attack and provide dimensional stability to gametangiophores. Our results suggest that at least some microfossils identified as nematophytes may be the remains of early marchantioid liverworts similar in some ways to modern Marchantia and Conocephalum. PMID:15263095

Identification of Sporopollenin as the Outer Layer of Cell Wall in Microalga Chlorella protothecoides.

PubMed

He, Xi; Dai, Junbiao; Wu, Qingyu

2016-01-01

Chlorella protothecoides has been put forth as a promising candidate for commercial biodiesel production. However, the cost of biodiesel remains much higher than diesel from fossil fuel sources, partially due to the high costs of oil extraction from algae. Here, we identified the presence of a sporopollenin layer outside the polysaccharide cell wall; this was evaluated using transmission electron microscopy, 2-aminoethanol treatment, acetolysis, and Fourier Transform Infrared Spectroscopy. We also performed bioinformatics analysis of the genes of the C. protothecoides genome that are likely involved in sporopollenin synthesis, secretion, and translocation, and evaluated the expression of these genes via real-time PCR. We also found that that removal of this sporopollenin layer greatly improved the efficiency of oil extraction.

Preservation of cycad and Ginkgo pollen

USGS Publications Warehouse

Frederiksen, N.O.

1978-01-01

Pollen grains of Ginkgo, Cycas, and Encephalartos were chemically treated together with pollen of Quercus, Alnus, and Pinus, the latter three genera being used as standards. The experiments showed that: (1) boiling the pollen for 8-10 hours in 10% KOH had little if any effect on any of the grains; (2) lengthy acetolysis treatment produced some degradation or corrosion, particularly in Ginkgo and Cycas, but the grains of even these genera remained easily recognizable; (3) oxidation with KMnO4 followed by H2O2 showed that pollen of Ginkgo, Cycas, and Encephalartos remains better preserved than that of Quercus and Alnus, and although Ginkgo and Encephalartos probably are slightly less resistant to oxidation than Pinus, no great differences exists between these monosulcate types and Pinus. Thus the experiments show that, at least for sediments low in bacteria, cycad and Ginkgo pollen should be well represented in the fossil record as far as their preservational capabilities are concerned. ?? 1978.

The contact site A glycoprotein of Dictyostelium discoideum carries a phospholipid anchor of a novel type.

PubMed Central

Stadler, J; Keenan, T W; Bauer, G; Gerisch, G

1989-01-01

The contact site A glycoprotein, a cell adhesion protein of aggregating Dictyostelium cells, was labeled with fatty acid, myo-inositol, phosphate and ethanolamine in vivo, indicating that the protein is anchored in the membrane by a lipid. This lipid was not susceptible to phosphatidyl inositol specific phospholipase C. When cleaved with nitrous acid or when subjected to acetolysis, the anchor released lipids which were different from those released from Trypanosoma variant cell surface glycoprotein, a protein with a known phosphatidyl inositol-glycan anchor. Resistance to weak and sensitivity to strong alkali indicated that the fatty acid in the contact site A glycolipid anchor was in an amide bond. On incubation with sphingomyelinase, a lipid with the chromatographic behavior of ceramide was released. These results suggest that the contact site A glycoprotein is anchored by a ceramide based lipid glycan. Images PMID:2721485

Determination of the structure of lecithins via the formation of acetylated 1,2-diglycerides.

PubMed

Privett, O S; Nutter, L J

1967-03-01

A detailed procedure for quantitative determinations of molecular species of lecithins is described and applied to several lecithins isolated from natural sources. The method is based on the conversion of lecithin to acetylated 1,2-diglycerides and analysis of these compounds by methodology used for the determination of triglyceride structure.The preparation of the acetylated 1,2-diglycerides was carried out via hydrolysis with phospholipase C and acetylation of the resultant, 1,2-diglycerides with pyridine-acetic anhydride. Preparation of acetylated 1,2-diglycerides from lecithin by acetolysis with acetic acid-acetic anhydride was shown to be accompanied by intermolecular as well as intramolecular rearrangement of the fatty acids.The structure of the acetylated 1,2-diglycerides was determined by a combination of argentation-TLC and pancreatic lipase hydrolysis using internal standards for quantification. The method was applied to lecithins isolated from milk serum, egg, soybean, safflower seed and wheat germ lipids.

Synthesis of novel 3'-azido-3'-deoxy-α-L-ribo configured nucleosides: A comparative study between chemical and chemo-enzymatic methodologies.

PubMed

Rana, Neha; Kumar, Manish; Singh, Ankita; Maity, Jyotirmoy; Shukla, Poonam; Prasad, Ashok K

2018-05-03

Syntheses of novel 3'-azido-3'-deoxy-2'-O,4'-C-methylene-α-L-ribofuranosyl nucleosides have been carried out from 3'-azido-3'-deoxy-4'-C-hydroxymethyl-β-D-xylofuranosyl nucleosides following both chemical and chemo-enzymatic methodologies. The precursor nucleoside in turn was synthesized from a common glycosyl donor 4-C-acetoxymethyl-1,2,5-tri-O-acetyl-3-azido-3-deoxy-α,β-D-xylofuranose, which was obtained by the acetolysis of 4-C-acetoxymethyl-5-O-acetyl-3-azido-3-deoxy-1,2-O-isopropylidene-α-D-xylofuranose in 96% yield. It has been observed that a chemo-enzymatic pathway for the synthesis of targeted nucleosides is much more efficient than a chemical pathway, leading to the improvement in yield for the synthesis of 3'-azido-3'-deoxy-α-L-ribofuranosyl thymine and uracil from 49 to 89% and 55 to 93%, respectively.

Occurrence of carotenoids and sporopollenin in Nanochlorum eucaryotum, a novel marine alga with unusual characteristics.

PubMed

Geisert, M; Rose, T; Bauer, W; Zahn, R K

1987-01-01

Pigment analysis of Nanochlorum eucaryotum on two strains grown under different gaseous conditions was performed. Air-gassed control cultures did not differ qualitatively with respect to the content of chlorophylls a and b, carotenes alpha and beta, lutein, violaxanthin, neoxanthin and cryptoxanthin in comparison with cultures grown under natural gas. The absolute pigment content per cell increased in cultures grown with natural gas. Growth of N. eucaryotum depends on CO2 which is present in concentrations up to 2.0 vol% in natural gas. N. eucaryotum cannot utilize methane and is therefore not methylotrophic. In cultures of N. eucaryotum grown with natural gas and in air-gassed cultures under nitrogen deficient conditions the secondary carotenoids canthaxanthin and astaxanthin could be detected. In air-gassed cultures of strain N. eucaryotum Colona the same secondary carotenoids have been found, while secondary carotenoids were never found in strain N. eucaryotum Mainz. Cell walls of N. eucaryotum always contain sporopollenin as confirmed by isolation, elemental analysis, infrared absorption spectrophotometry, acetolysis-resistance and electron microscopy.

Visualization of sporopollenin-containing pathogenic green micro-alga Prototheca wickerhamii by fluorescent in situ hybridization (FISH).

PubMed

Ueno, Ryohei

2009-04-01

Fluorescent in situ hybridization (FISH) using taxon-specific, rRNA-targeted oligonucleotide probes is one of the most powerful tools for the rapid identification of harmful microorganisms. However, eukaryotic algal cells do not always allow FISH probes to permeate over their cell walls. Members of the pathogenic micro-algal genus Prototheca are characterized by their distinctive cell-wall component, sporopollenin, an extremely tough biopolymer that resists acid and alkaline hydrolysis, enzyme attack, and acetolysis. To our knowledge, there has been no report of the successful permeation by the oligonucleotide probes over the cell walls of unicellular green micro-algae, which contain sporopollenin. The DNA probes passed through the cell wall of Prototheca wickerhamii after treating the algal cells with cetyltrimethylammonium bromide (CTAB). Most cells in the middle logarithmic growth phase culture fluoresced when hybridized with the rRNA-targeted universal probe for eukaryotes, though individual cells included in this culture differed in the level of cell-wall vulnerability to attack by the polysaccharide-degrading enzyme, thus reflecting the different stages of the life cycle. This is the first report regarding the visualization of sporopollenin-containing, green micro-algal cells by FISH.

Pollen analysis in honey samples from the two main producing regions in the Brazilian northeast.

PubMed

Sodré, Geni da S; Marchini, Luís C; Carvalho, Carlos A L de; Moreti, Augusta C de C C

2007-09-01

Knowledge about the botanical source of honey is very important for the beekeeper while it indicates adequate and abundant supply sources of nectar and pollen for the bees, thus contributing toward improved yield. The present study means to identify the pollen types occurring in 58 samples of honey produced in two states of the northeastern region of Brazil, Piauí (38 samples) and Ceará (20 samples), and to verify the potential of the honey plants during the months of February to August. The samples were obtained directly from beekeepers in each state and analyzed at the Apiculture Laboratory of the Entomology Section of Escola Superior de Agricultura "Luiz de Queiroz", USP, Piracicaba, State of São Paulo, Brazil. The pollen analysis was performed using the acetolysis method. The samples were submitted to both a qualitative and a quantitative analysis. The dominant pollen in the State of Ceará is from Mimosa caesalpiniaefolia, M. verrucosa, Borreria verticillata, Serjania sp., and a Fabaceae pollen type, while in the State of Piauí it is from Piptadenia sp., M. caesalpiniaefolia, M. verrucosa, Croton urucurana and Tibouchina sp.

Chemical and immunological characterization of the extracellular galactomannan of Aspergillus fumigatus.

PubMed Central

Latgé, J P; Kobayashi, H; Debeaupuis, J P; Diaquin, M; Sarfati, J; Wieruszeski, J M; Parra, E; Bouchara, J P; Fournet, B

1994-01-01

The galactomannan (GM) produced extracellularly by Aspergillus fumigatus has been purified by a double sequential hydrazine-nitrous acid treatment of the ethanol precipitate of the culture filtrate. Nuclear magnetic resonance and gas-liquid chromatography-mass spectrometry analysis have been performed on intact GM, acid-hydrolyzed GM, and oligomers resulting from the acetolysis of the acid-hydrolyzed GM. Results show that A. fumigatus GM is composed of a linear mannan core with an alpha-(1-2)-linked mannotetraose repeating unit attached via alpha-(1-6) linkage. Side chains composed of an average of 4 to 5 beta-(1-5)-galactofuranose units are linked to C-6 and C-3 positions of alpha-(1-2)-linked mannose units of the mannan. The immunoreactivity of GM and HCl-hydrolyzed GM was studied by use of human sera from aspergillosis patients and an antigalactofuran monoclonal antibody. The alpha-(1-2) (1-6)-mannan core is not antigenic. The immunogenic galactofuran is found amongst several exocellular glycoproteins. According to a direct enzyme-linked immunosorbent assay with GM as the detector antigen, only 26% of the serum samples from aspergilloma patients (all positive by immunodiffusion assays) give optical density values superior to a cutoff estimated as the mean +/- 3 standard deviations of values obtained with control sera. Images PMID:7960122

Pollen characters of Firmiana malayana Kostem. (Malvaceae: Sterculoideae) in Malaysia

NASA Astrophysics Data System (ADS)

Amirul-Aiman, A. J.; Noraini, T.; Nurul-Aini, C. A. C.; Idris, S.; Suhaniza, R.

2018-04-01

Firmiana malayana also known as "Bullocks eye or Mata Lembu" in Malaysia and can be found along riverbanks and open forests in Peninsular Malaysia and seldom planted in populated areas. The flowers of the Firmiana malayana are vivid orange in colour, on tassels up to 12 cm long. Usually this species will shed its leaves after a dry period and remains bare for six to eight weeks. The objective of this study is to determine the pollen morphological characteristics of the Firmiana malayana in order to add more information on the species under the family of Sterculiaceae in Malaysia. Methods for this study includes acetolysis technique for the pollens and viewed under light microscope and scanning electron microscope. Results shown that the pollens of the species Firmiana malayana appeared to be monad and dyad with tricolporate class with both porate and colpus present. The shape of this species is prolate with P/E index of 1.49. This species was considered as medium-size pollens as the pollens ranges from 26 - 36 µm. The ornamentation of the pollen is reticulate where the ornamentation is network-like pattern formed by exine elements of lumen and murus. Based on the results obtained, pollen morphology is a great tool that can aid in plant identification and classification as well having taxonomic values.

Pollen morphology of Rhizophora L. in Peninsular Malaysia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohd-Arrabe', A. B.; Noraini, Talip Noraini

Rhizophora L. are common mangrove genus in Peninsular Malaysia, it contains 3 species and 1 hybrid (R. apiculata Blume, R. mucronata Lam., R. stylosa Griff., R. x lamarckii Montrouz). This genus has some unique adaptation towards extreme environment. Rhizophora has looping aerial stilt-root and uniformly viviparous. The aim of this study is to investigate the variation in the pollen morphology of Rhizophora that can be related to their habitat. Methods include in this study is pollen observation under light and acetolysis method under scanning electron microscope. Pollen type of Rhizophora species studied except hybrid species is classified tricolporate, shape spheroidalmore » based on ratio of length polar axis/ length of equatorial axis (1.03 - 1.09). The exine ornamentation is perforate-reticulate for R. apiculata and R. mucronata, while R. stylosa is perforate. For the only hybrid in Peninsular Malaysia, R. x lamarckii (R. apiculata x R. stylosa) differs from others, tricolpate with the absence of porate, shape is subprolate and exine ornamentation is reticulate and striate in equatorial region. Pollenkitt is present due to the salty and extreme environment. This may enhance the volume of pollenkitt present surrounding the pollen grains in Rhizophora for protection and adaptation purposes. Based on these findings, it is evident that pollen morphology is somehow related to its natural habitat.« less

Pollen morphology of Rhizophora L. in Peninsular Malaysia

NASA Astrophysics Data System (ADS)

Mohd-Arrabe', A. B.; Noraini, Talip Noraini

2013-11-01

Rhizophora L. are common mangrove genus in Peninsular Malaysia, it contains 3 species and 1 hybrid (R. apiculata Blume, R. mucronata Lam., R. stylosa Griff., R. x lamarckii Montrouz). This genus has some unique adaptation towards extreme environment. Rhizophora has looping aerial stilt-root and uniformly viviparous. The aim of this study is to investigate the variation in the pollen morphology of Rhizophora that can be related to their habitat. Methods include in this study is pollen observation under light and acetolysis method under scanning electron microscope. Pollen type of Rhizophora species studied except hybrid species is classified tricolporate, shape spheroidal based on ratio of length polar axis/ length of equatorial axis (1.03 - 1.09). The exine ornamentation is perforate-reticulate for R. apiculata and R. mucronata, while R. stylosa is perforate. For the only hybrid in Peninsular Malaysia, R. x lamarckii (R. apiculata x R. stylosa) differs from others, tricolpate with the absence of porate, shape is subprolate and exine ornamentation is reticulate and striate in equatorial region. Pollenkitt is present due to the salty and extreme environment. This may enhance the volume of pollenkitt present surrounding the pollen grains in Rhizophora for protection and adaptation purposes. Based on these findings, it is evident that pollen morphology is somehow related to its natural habitat.

[Pollen analysis of the post-emergence residue of Centris tarsata Smith (Hymenoptera: Apidae, Centridini) nests].

PubMed

Dórea, Marcos da C; Dos Santos, Francisco de A R; Lima, Luciene C de L E; Figueroa, Luís E R

2009-01-01

A new treatment protocol was developed to analyze pollen residues found in nests of Centris tarsata Smith harvested from nest-traps. The study area was located in the Canudos Biological Station in the municipality of Canudos (09 masculine56'34'S; 38 masculine59'17'W), in the northeastern micro-region of Bahia State, Brazil. The local vegetation is an open caatinga (deciduous dryland vegetation), the regional climate is semi-arid, the average annual temperature is 24.1 masculineC, and the annual regional rainfall rate is 454 mm. Ten nests of C. tarsata were collected in trap-nests during the first semester of 2004. Pollen analysis from the nests required the development of a new methodology that combined techniques of palynological sediment analysis with the more common pollinic analysis by acetolysis. Microscopic analyses employed optical microscopy techniques. The pollinic spectrum of the samples from C. tarsata indicated the presence of 17 pollen types from seven plant families, which were present in assemblage of five to eleven pollen types, pointed to the plants used by bees to feed on their offspring. The most represented plant families were Leguminosae (49.3%) and Solanaceae (43.2%). The most frequent pollen types in the samples were from Solanum paniculatum (43.8%) and Senna rizzini (32.1%). The protocol developed provides a new tool for diet assessment of Centris and other groups of solitary bees.

PpASCL, the Physcomitrella patens Anther-Specific Chalcone Synthase-Like Enzyme Implicated in Sporopollenin Biosynthesis, Is Needed for Integrity of the Moss Spore Wall and Spore Viability

PubMed Central

Daku, Rhys M.; Rabbi, Fazle; Buttigieg, Josef; Coulson, Ian M.; Horne, Derrick; Martens, Garnet; Ashton, Neil W.; Suh, Dae-Yeon

2016-01-01

Sporopollenin is the main constituent of the exine layer of spore and pollen walls. The anther-specific chalcone synthase-like (ASCL) enzyme of Physcomitrella patens, PpASCL, has previously been implicated in the biosynthesis of sporopollenin, the main constituent of exine and perine, the two outermost layers of the moss spore cell wall. We made targeted knockouts of the corresponding gene, PpASCL, and phenotypically characterized ascl sporophytes and spores at different developmental stages. Ascl plants developed normally until late in sporophytic development, when the spores produced were structurally aberrant and inviable. The development of the ascl spore cell wall appeared to be arrested early in microspore development, resulting in small, collapsed spores with altered surface morphology. The typical stratification of the spore cell wall was absent with only an abnormal perine recognisable above an amorphous layer possibly representing remnants of compromised intine and/or exine. Equivalent resistance of the spore walls of ascl mutants and the control strain to acetolysis suggests the presence of chemically inert, defective sporopollenin in the mutants. Anatomical abnormalities of late-stage ascl sporophytes include a persistent large columella and an air space incompletely filled with spores. Our results indicate that the evolutionarily conserved PpASCL gene is needed for proper construction of the spore wall and for normal maturation and viability of moss spores. PMID:26752629

A novel synthesis of acyclonucleosides via allylation of 3-[1-(phenylhydrazono)-L-threo-2,3,4-trihydroxybut-1-yl]quinoxalin-2(1H)one.

PubMed

Hamid, Hamida Mohamed Abdel

2003-10-31

The allylation of 3-[1-(phenylhydrazono)-L-threo-2,3,4-trihydroxybut-1-yl]quinoxalin-2(1H)one (1) gave, in addition to the anticipated 1-N-allyl derivative (2), a dehydrative cyclized product, 1-N-allyl-3-[5-(hydroxymethyl)-1-phenylpyrazol-3-yl]quinoxalin-2-one (4) and its isomeric O-allyl derivative 3. The O-allyl group in 3 underwent acetolysis under acetylation conditions, in addition to the acetylation of the hydroxyl group, to afford 2-acetoxy-3-[5-(acetoxymethyl)-1-phenylpyrazol-3-yl]quinoxaline (8) instead of the O-acetyl derivative of 3. Allylation of the tri-O-acetyl derivative of 1 caused the elimination of a molecule of acetic acid in addition to N-allylation to give 1-N-allyl-3-[3,4-di-O-acetyl-2-deoxy-1-(phenylhydrazono)but-2-en-1-yl]quinoxalin-2-one (11). Hydroxylation of the allyl group gave a glycerol-1-yl acyclonucleoside which can be alternatively obtained by a displacement reaction of the tosyloxy group in 2,3-O-isopropylidene-1-O-(p-tolylsulfonyl)glycerol (14), followed by deisopropylidenation. 1-N-(2,3-Dibromopropyl)-3-[5-(hydroxymethyl)-1-(4-bromophenyl)pyrazol-3-yl]quinoxalin-2-one (15) underwent azidolysis to give a 2,3-diazido derivative. The assigned structures were based on spectral analysis. The activity of compounds 2, 4, 6, and 15 against hepatitis B virus was studied.

A precursor to the beta-pyranosides of 3-amino-3,6-dideoxy-D-mannose (mycosamine).

PubMed

Alais, J; David, S

1992-06-04

SN2-type reaction of 3-O-(1-imidazyl)sulfonyl-1,2:5,6-di-O-isopropylidene-alpha-D-gluco furanose with benzoate gave the 3-O-benzoyl-alpha-D-allo derivative 2, which was hydrolysed to give the 5,6-diol 3. Compound 3 was converted into the 6-deoxy-6-iodo derivative 4 which was reduced with tributylstannane, and then position 5 was protected by benzyloxymethylation, to give 3-O-benzoyl-5-O-benzyloxymethyl-6-deoxy-1,2-O-isopropylidene-alpha -D- allofuranose (6). Debenzoylation of 6 gave 7, (1-imidazyl)sulfonylation gave 8, and azide displacement gave 3-azido-5-O-benzyloxymethyl-3,6-dideoxy- 1,2-O-isopropylidene-alpha-D-glucofuranose (9, 85%). Acetolysis of 9 gave 1,2,4-tri-O-acetyl-3-azido-3,6-dideoxy-alpha,beta-D-glucopyranose (10 and 11). Selective hydrolysis of AcO-1 in the mixture of 10 and 11 with hydrazine acetate (----12), followed by conversion into the pyranosyl chloride 13, treatment with N,N-dimethylformamide dimethyl acetal in the presence of tetrabutylammonium bromide, and benzylation gave 3-azido-4-O-benzyl-3,6-dideoxy-1,2-O-(1-methoxyethylidene)-alpha-D -glucopyranose (15). Treatment of 15 with dry acetic acid gave 1,2-di-O-acetyl-3-azido-4-O-benzyl-3,6-dideoxy-beta-D-glucopyranose (16, 86% yield) that was an excellent glycosyl donor in the presence of trimethylsilyl triflate, allowing the synthesis of cyclohexyl 2-O-acetyl-3-azido-4-O-benzyl-3,6-dideoxy-beta-D-glucopyranoside (17, 90%).(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental and ultrastructural characters of the pollen grains and tapetum in species of Nymphaea subgenus Hydrocallis.

PubMed

Zini, Lucía Melisa; Galati, Beatriz Gloria; Zarlavsky, Gabriela; Ferrucci, María Silvia

2017-07-01

Variations in pollen characters and tapetum behavior were recently acknowledged in the early-divergent family Nymphaeaceae and even within the genus Nymphaea, which probably is not monophyletic; some traits such as infratectum and tapetum type are also a matter of different interpretations. In this study, developmental characters of the pollen grains and tapetum in Nymphaea subgenus Hydrocallis are provided for the first time. Observations were made in N. amazonum, N. gardneriana, and N. prolifera using light, scanning, and transmission electron microscopy. Tapetum is of the secretory type and produces orbicules. At microspore and pollen grain stages, the distal and proximal walls differ considerably. This result supports the operculate condition of the aperture in Hydrocallis, and such aperture might be plesiomorphic for Nymphaeoideae. The infratectum is intermediate, composed of inter-columellae granular elements, robust columellae consisting of agglomerated granules, complete columellae, and fused columellae. Narrow microchannels are present and persist until the mature pollen grain stage. The membranous granular layer is often present in the pollen grains of Nymphaeaceae. In N. gardneriana, this layer is most probably a component of the intine because it is lost after acetolysis. Orbicules in the Nymphaeaceae are characterized as spherical or subspherical, with a smooth sporopolleninic wall that surrounds an electron-lucent core and with individual orbicules that usually merge to give irregular aggregations. The aperture, pollen wall ultrastructure, and the tapetum of the studied species are discussed in an evolutionary and systematic context, and these characters are also compared with those of other angiosperm lineages.