Recycling organic residues in soils as amendments: Effect on the mobility of two herbicides under different management practices.

The addition of organic residues to soil to increase its organic matter content is considered as a viable option for sustainable food production in soils sensitive to degradation and erosion. However, the recycling of these organic residues in agricultural soils needs to be previously appraised because they can modify the behaviour of pesticides when they are simultaneously applied in agricultural practices. This study evaluated the changes in the mobility and persistence of two herbicides, triasulfuron and prosulfocarb, after two repeated applications in field experimental plots in an unamended soil and one amended with green compost (GC) for seven months. Different factors were studied: i) soil without amendment (S), ii) soil amended with two doses of GC (∼12 t C ha-1, S + GC1 and 40 t C ha-1, S + GC2), and iii) soils unamended and amended with different irrigation conditions: non-irrigated and with additional irrigation (2.8 mm per week). After the first application of herbicides, the results initially indicated no significant effects of soil treatments or irrigation conditions for triasulfuron mobility in agreement with the residual concentrations in the soil profile. The effect of irrigation was noted after one month of herbicide application and the effect of the soil treatment was significant after two months because the persistence of triasulfuron in S + GC2 was maintained until 50% of the applied amount. For prosulfocarb, the influence of soil amendment was significant for the initial persistence of the herbicide in S + GC2, higher than in S or S + GC1, in agreement with its adsorption constants for this soil. However, dissipation or leaching of the herbicide over time was not inhibited in this soil. After the repeated application of herbicides, the influence of the treatment of soils and/or irrigation was significant for the leaching and dissipation of both herbicides. The initial dissipation/degradation or leaching of herbicides was higher than after the first application, although persistence was maintained after five months of application in amended soils for triasulfuron and in unamended and amended soils for prosulfocarb. The results confirm that high doses of GC increased the persistence of both herbicides. This practice may offer the possibility of applying a tailored dose of GC to soil for striking a balance between residual concentrations and the soil agronomic effect.

Application of green compost as amendment in an agricultural soil: Effect on the behaviour of triasulfuron and prosulfocarb under field conditions.

Herbicides are essential in agricultural systems for maintaining crop yields, as weeds compromise grain production. Furthermore, the application of organic amendments to soil is an increasingly frequent agricultural practice for avoiding irreversible soil degradation. However, this practice could modify the behaviour of the herbicides applied, with implications for their absorption by weeds. This study evaluated the dissipation, persistence and mobility of the herbicides triasulfuron and prosulfocarb in a sandy clay loam soil unamended and amended with green compost (GC) in a field experiment using single or combined commercial formulations of both herbicides. The study was carried out in experimental plots (eight treatments × three replicates) corresponding to unamended soil and soil amended with GC, untreated and treated with the herbicide formulations Logran®, Auros® and Auros Plus® over 100 days. The half-life (DT50) of triasulfuron applied individually was 19.4 days, and increased in the GC-amended soil (46.7 days) due to its higher adsorption by this soil, although non-significant differences between DT50 values were found when it was applied in combination with prosulfocarb. Prosulfocarb dissipated faster than triasulfuron under all the conditions assayed, but non-significant differences were observed for the different treatments. The analysis of the herbicides at different soil depths (0-50 cm) after their application confirmed the leaching of both herbicides to deeper soil layers under all conditions, although larger amounts of residues were found in the 0-10 and 10-20 cm layers. The application of GC to the soil increased the persistence of both herbicides, and prevented the rapid leaching of triasulfuron in the soil, but the leaching of prosulfocarb was not inhibited. The influence of single or combined formulations was observed for triasulfuron, but not for prosulfocarb. The results obtained highlight the interest of obtaining field data to design rational joint applications of GC and herbicides to prevent the possible decrease in their effectiveness for weeds or the risk of water contamination.

Biophysics and protein corona analysis of Janus cyclodextrin-DNA nanocomplexes. Efficient cellular transfection on cancer cells.

The self-assembling processes underlining the capabilities of facially differentiated ("Janus") polycationic amphiphilic cyclodextrins (paCDs) as non-viral gene nanocarriers have been investigated by a pluridisciplinary approach. Three representative Janus paCDs bearing a common tetradecahexanoyl multitail domain at the secondary face and differing in the topology of the cluster of amino groups at the primary side were selected for this study. All of them compact pEGFP-C3 plasmid DNA and promote transfection in HeLa and MCF-7 cells, both in absence and in presence of human serum. The electrochemical and structural characteristics of the paCD-pDNA complexes (CDplexes) have been studied by using zeta potential, DLS, SAXS, and cryo-TEM. paCDs and pDNA, when assembled in CDplexes, render effective charges that are lower than the nominal ones. The CDplexes show a self-assembling pattern corresponding to multilamellar lyotropic liquid crystal phases, characterized by a lamellar stacking of bilayers of the CD-based vectors with anionic pDNA sandwiched among them. When exposed to human serum, either in the absence or in the presence of pDNA, the surface of the cationic CD-based vector becomes coated by a protein corona (PC) whose composition has been analyzed by nanoLC-MS/MS. Some of the CDplexes herein studied showed moderate-to-high transfection levels in HeLa and MCF-7 cancer cells combined with moderate-to-high cell viabilities, as determined by FACS and MTT reduction assays. The ensemble of data provides a detail picture of the paCD-pDNA-PC association processes and a rational base to exploit the protein corona for targeted gene delivery on future in vivo applications.

Study of processes influencing bioavailability of pesticides in wood-soil systems: Effect of different factors.

Lignocellulosic wastes and by-products containing lignin are now available in large amounts from forestry and industrial activities, and could be promising organic materials for the biosorption of pesticides by soils in order to reduce point-source pollution. Adding these materials to soil requires understanding the process of pesticide sorption-desorption by wood-soils, as sorption capacity could increase, with changes in pesticide bioavailability and final fate. The objective of this work was to study the effect that pine and oak wood added to soils had on the sorption/desorption of the pesticides linuron, alachlor, and metalaxyl. Experiments were conducted with two sandy loam and sandy clay soils each amended with two wood doses (5% and 50%) after different incubation times (0, 5 and 12 months). A low wood dose (5%) had no significant impact on the sorption (Kf) of alachlor, but Kf increased for linuron (up to 5.4-1.7 times) and metalaxyl (up to 4.4 and 8.6 times) in all wood-soil systems. The results were not significantly different after different incubation times. The desorption results indicated that wood decreases the sorption irreversibility of alachlor, and increases that of linuron and metalaxyl, with a varying effect of the wood-soil incubation time. The addition of a high wood dose to soil (50%) was more significant for increasing the sorption of all the pesticides, and the sorbed amounts remaining after desorption (>49% for linuron, >33% for alachlor and >6% for metalaxyl), although there was no apparent discrimination between the two types of woods. The role of the nature of the organic carbón (Koc values) for sorption was evidenced for alachlor and metalaxyl, but not for linuron. These outcomes are of interest for extending wood application to soil as a barrier for avoiding environmental risk by point-source pollution due to the use and management of pesticides in farming systems.

Human leucocyte antigen (HLA)-DQB1*03:02 and HLA-A*02:01 have opposite patterns in their effects on susceptibility to HIV infection.

OBJECTIVES: The objective of this study was to seek correlates of immune protection in HIV infection. We sought to elucidate the association between the presence of human leucocyte antigen (HLA) alleles, as well as killer immunoglobulin receptor (KIR) genotypes, and the susceptibility to HIV infection in a Spanish cohort of HIV-exposed seronegative (HESN) individuals. METHODS: A total of 152 individuals were evaluated: 29 HESN individuals in stable heterosexual relationships with an HIV-infected partner admitting high-risk sexual intercourse for at least 12 months prior to inclusion in the study, 61 HIV-infected patients and 62 healthy controls. HLA class I and II alleles and KIR genotypes were assessed in genomic DNA from all individuals in the study by polymerase chain reaction-sequence-specific oligonucleotide (PCR-SSO) using bead array technology. RESULTS: HESN individuals showed a higher prevalence of HLA-A3 (62%) and HLA-B44 (83%) supertypes compared with HIV-infected individuals (42% and 66%, respectively). Regarding specific HLA alleles, HESN individuals had a higher prevalence of HLA-A*33:01, DRB1*04 and DQB1*03:02 alleles (14%, 34% and 31%, respectively) and a lower prevalence of the HLA-A*02:01 allele (27%) than HIV-infected patients (3%, 15%, 11% and 52%, respectively; P < 0.05). Interestingly, in a multivariate analysis, only the presence of DQB1*03:02 and the absence of A*02:01 alleles were independently associated with HESN status [odds ratio (OR) 3.4 (95% confidence interval (CI) 1.1-10.5) and 0.4 (95% CI: 0.1-0.9), respectively; P < 0.05]. No KIR genotype was associated with susceptibility to HIV infection. CONCLUSIONS: Our data showed that the presence of the HLA class II allele DQB1*03:02 was a correlate of immune protection against HIV infection, while the presence of the HLA class I allele A*02:01 was associated with being infected with HIV.

Field versus laboratory experiments to evaluate the fate of azoxystrobin in an amended vineyard soil.

This study reports the effect that adding spent mushroom substrate (SMS) to a representative vineyard soil from La Rioja region (Spain) has on the behaviour of azoxystrobin in two different environmental scenarios. Field dissipation experiments were conducted on experimental plots amended at rates of 50 and 150 t ha(-1), and similar dissipation experiments were simultaneously conducted in the laboratory to identify differences under controlled conditions. Azoxystrobin dissipation followed biphasic kinetics in both scenarios, although the initial dissipation phase was much faster in the field than in the laboratory experiments, and the half-life (DT50) values obtained in the two experiments were 0.34-46.3 days and 89.2-148 days, respectively. Fungicide residues in the soil profile increased in the SMS amended soil and they were much higher in the top two layers (0-20 cm) than in deeper layers. The persistence of fungicide in the soil profile is consistent with changes in azoxystrobin adsorption by unamended and amended soils over time. Changes in the dehydrogenase activity (DHA) of soils under different treatments assayed in the field and in the laboratory indicated that SMS and the fungicide had a stimulatory effect on soil DHA. The results reveal that the laboratory studies usually reported in the literature to explain the fate of pesticides in amended soils are insufficient to explain azoxystrobin behaviour under real conditions. Field studies are necessary to set up efficient applications of SMS and fungicide, with a view to preventing the possible risk of water contamination.

Comparison of three pesticide fate models with respect to the leaching of two herbicides under field conditions in an irrigated maize cropping system.

The ability of three models (PEARL, MACRO and PRZM) to describe the water transfer and leaching of the herbicides S-metolachlor and mesotrione as observed in an irrigated maize monoculture system in Toulouse area (France) was compared. The models were parameterized with field, laboratory and literature data, and pedotransfer functions using equivalent parameterization to better compare the results and the performance of the models. The models were evaluated and compared from soil water pressure, water content and temperature data monitored at 0.2, 0.5 and 1 m depth, together with water percolates and herbicide concentrations measured in a tension plate lysimeter at 1 m depth. Some hydraulic (n, θ(s)) parameters and mesotrione DT50 needed calibration. After calibration, the comparison of the results obtained by the three models indicated that PRZM was not able to simulate properly the water dynamic in the soil profile. On the contrary, PEARL and MACRO simulated generally quite well the observed water pressure head and volumetric water content at the three different depths during wetting periods (e.g. irrigated cropping period) while a poorest performance was obtained for drying periods (fallow period with bare soil and beginning of crop period). Similar water flow dynamics were simulated by PEARL and MACRO in the soil profile although in general, and due to a higher evapotranspiration in MACRO, PEARL simulated a wetter soil than MACRO. For the whole simulated period, the performance of all models to simulate water leaching at 1m depth was poor, with an overestimation of the total water volume measured in the lysimeter (ranging from 2.2 to 6.6 times). By contrast, soil temperature was properly reproduced by the three models. The models were able to simulate the leaching of herbicides at 1m depth in similar appearance time and order of magnitude as field observations. Cumulative observed and simulated mesotrione losses by leaching were consistently higher than the observed and simulated losses of the less mobile herbicide, S-metolachlor. In general, PRZM predicted the highest concentrations for both herbicides in the leachates while PEARL simulated the observed herbicide concentrations better than MACRO and PRZM.

European mitochondrial haplogroups are not associated with hepatitis C virus (HCV) treatment response in HIV/HCV-coinfected patients.

OBJECTIVES: Mitochondria are multifunctional organelles with a key role in the innate immune response against viral infections. Mitochondrial DNA (mtDNA) haplogroups have been related to AIDS progression and CD4 T-cell recovery in HIV-infected patients, and to a delay in the development of liver fibrosis in HIV/hepatitis C virus (HCV)-coinfected patients. We performed a study to investigate whether mtDNA haplogroups may be associated with HCV treatment response in HIV/HCV-coinfected patients on pegylated interferon (pegIFN) plus ribavirin (RBV). METHODS: We performed a retrospective study in 304 patients who completed a course of HCV therapy. mtDNA polymorphisms were genotyped using Sequenom's MassARRAY platform. The interleukin-28B (IL-28B) polymorphism (rs12980275) was genotyped using the GoldenGate® assay. Sustained virological response (SVR) was defined as an undetectable HCV viral load at week 24 after the end of treatment. The statistical analysis was carried out using on-treatment data. RESULTS: The SVR rates were 52.6% (160 of 304) for all patients, and 37.8% (46 of 201) for patients with HCV genotype 1 or 4 vs. 81.4% (83 of 102) for patients with HCV genotype 2 or 3 (P < 0.001). No significant associations were found between mtDNA haplogroup and SVR when all patients were included in the analysis and when patients were stratified by HCV genotype (i.e. those with genotypes 1/4 and 2/3 analysed separately) or IL-28B rs12980275 genotype. CONCLUSIONS: European mtDNA haplogroups were not related to HCV treatment response in HIV/HCV-coinfected patients on pegIFN-α/RBV therapy.

Recent developments on synthetic tools towards structural and functional glycodiversity.

Despite being the most abundant type of biopolymers in Nature, the biological relevance of carbohydrates has systematically been underrated for decades, associating them far less sophisticated functions (structural or energy sourcing) than those unraveled for polynucleotides and proteins. The inherently large and complex diversity of carbohydrates and glycoconjugates, together with the lack of efficient technologies to either isolate them from natural sources or produce them synthetically in useful amounts, have burdened the appreciation of their utmost importance in the most fundamental biological processes. For these reasons, carbohydrate-mediated transmission of biological information was largely unexplored. However, over the decades, it became clear that the expression of complex carbohydrates is critical in the development of living systems. Nature uses this diverse repertoire of structures as codes in fundamental biological processes such as cellular differentiation, cellular signaling, fertilization or immune response, among many others. The urgency to elucidate the glycan code in terms of structure-function relationships has fuelled chemical biology approaches uncovering new frontiers in molecular biology, for which the term glycobiology had to be coined in the early 1980s'. Novel strategies for assembling oligosaccharides, glycoproteins, glycolipids and a range of glycoconjugates have flourished ever since providing access to glycomaterials for interrogating and interfering glycan function. This account focuses on the major breakthroughs made on the strategies during the last decades to synthetically reproduce the overwhelming glycodiversity, emphasizing on the dazzling array of concepts and techniques which development was required to cope with the task. In the first place, a succinct overview of the structural and functional diversity of biologically relevant saccharides and glycoconjugates will be given. Then, a selection of the most relevant strategies that composes the complex and diversity-oriented toolbox that modern carbohydrate synthesis consists on will be dissected. Finally, a selection of the most recent applications of this synthetic toolbox to chemical biology will be captured.

Use of raw or incubated organic wastes as amendments in reducing pesticide leaching through soil columns.

Soil amendment with organic wastes is becoming a widespread management practice since it can effectively solve the problems of uncontrolled waste accumulation and improve soil quality. However, when simultaneously applied with pesticides, organic wastes can significantly modify the environmental behaviour of these compounds. This study evaluated the effect of sewage sludges (SS), grape marc (GM) and spent mushroom substrates (SMS) on the leaching of linuron, diazinon and myclobutanil in packed columns of a sandy soil with low organic matter (OM) content (<1%). Soil plus amendments had been incubated for one month (1 m) or 12 months (12 m). Data from the experimental breakthrough curves (BTCs) were fitted to the one-dimensional transport model CXTFIT 2.1. All three amendments reduced leaching of linuron and myclobutanil relative to unamended soil. SMS was the most effective in reducing leaching of these two compounds independent of whether soil was incubated for 1 m or 12 m. Soil amendments increased retardation coefficients (Rexp) by factors of 3 to 5 for linuron, 2 to 4 for diazinon and 3 to 5 for myclobutanil relative to unamended soil. Leaching of diazinon was relatively little affected by soil amendment compared to the other two compounds and both SS and SMS amendment with 1m incubation resulted in enhanced leaching of diazinon. The leaching data for linuron and myclobutanil were well described by CXTFIT (mean square error, MSE<4.9·10(-7) and MSE<7.0·10(-7), respectively) whereas those of diazinon were less well fitted (MSE<2.1·10(-6)). The BTCs for pesticides were similar in soils incubated for one month or one year, indicating that the effect of amendment on leaching persists over relatively long periods of time.

IL28RA polymorphism is associated with early hepatitis C virus (HCV) treatment failure in human immunodeficiency virus-/HCV-coinfected patients.

Due to the poor rate of response to hepatitis C virus (HCV) with pegylated interferon and ribavirin treatment in HCV/HIV coinfected patients, key factors for predicting failure would be useful. We performed a retrospective study on 291 patients on HCV treatment, who had early virological response (EVR) data. IL28B and IL28RA polymorphisms were performed using the GoldenGate(®) assay. Unfavourable genotypes at IL28B (rs12980275 AG/GG and rs8099917 GT/GG) and an unfavourable allele at IL28RA (rs10903035 G) were associated with early treatment failure. However, only the rs12980275 AG/GG genotype and rs10903035 G allele remained independently associated with early failure in the overall population (OR = 4.15 (95% CI = 1.64-10.54) and OR = 2.00 (95% CI = 1.19-3.36), respectively) as well as in GT1/4 patients (OR = 5.07 (95% CI = 1.81-14.22) and OR = 2.03 (95% CI = 1.13-3.66), respectively). Next, a decision tree showed early treatment failure increased from 37.1% to 65.5% when the unfavourable rs12980275 AG/GG and rs10903035 AG/GG genotypes and HCV-RNA≥ 500.000 IU/mL were taken into account in GT1/4 patients. In contrast, the failure rate decreased from 37.1% to 11.9% when the favourable rs12980275 AA and rs10903035 AA genotypes were detected. The percentage of patients correctly classified was 78.4%, and AUROC was 0.802 ± 0.028. Regarding GT3 patients, the presence of the GCGCA haplotype (all unfavourable alleles) was associated with early treatment failure, while no association was observed for the IL28B polymorphisms. In conclusion, the IL28RA polymorphism was associated with early treatment failure independently of the IL28B SNPs. The combination of IL28B and IL28RA polymorphisms might be a valuable tool for predicting early treatment failure before starting HCV treatment.

Level, phenotype and activation status of CD4+FoxP3+ regulatory T cells in patients chronically infected with human immunodeficiency virus and/or hepatitis C virus.

CD4(+) regulatory T (T(reg)) cells have been involved in impaired immunity and persistence of viral infections. Herein, we report the level, phenotype and activation status of T(reg) cells in patients chronically infected with human immunodeficiency virus (HIV) and/or hepatitis C virus (HCV). Expression of CD25, CD45RA, CD27, CD127 and CD38 was assessed on these cells using polychromatic flow cytometry in 20 healthy controls, 20 HIV-monoinfected, 20 HCV-monoinfected and 31 HIV/HCV-co-infected patients. T(reg) cells were defined as CD4(+)forkhead box P3 (FoxP3)(+). The percentage of T(reg) cells was increased significantly in HIV patients compared with controls. Moreover, there was a significant inverse correlation between CD4 counts and T(reg) cell levels. Fewer than 50% of T(reg) cells expressed CD25, with differences in terms of CD127 expression between CD25(+) and CD25((-)) T(reg) cells. CD4(+)Foxp3(+) T(reg) cells displayed predominantly a central memory phenotype (CD45RA(-)CD27(+)), without differences between patients and healthy controls. Activated T(reg) cells were increased in HIV patients, particularly considering the central memory subset. In summary, HIV infection, but not HCV, induces an up-regulation of highly activated T(reg) cells, which increases in parallel with CD4 depletion. Hypothetically, this might contribute to the accelerated course of HCV-related liver disease in HIV-immunosuppressed patients.

Hydroxyurea exerts an anti-proliferative effect on T cells but has no direct impact on cellular activation.

Hydroxyurea (HU) is a cytostatic drug which has been used as an anti-HIV agent due mainly to its synergistic activity when combined with certain anti-retrovirals. In addition, HU might have a beneficial effect on parameters involved in the pathogenesis of HIV infection, such as immune activation. To test this hypothesis, the effect of HU on T cell proliferation and T cell activation, as well as the potential association between these two phenomena, were examined in an in vitro model. HU exerted a dose-dependent anti-proliferative effect on T cells, and modulated the expression of different activation markers. In cells exposed to HU, expression of CD25 and CD38 diminished in a dose-dependent manner, whereas expression of CD69 increased. However, when the expression of these markers was examined separately on proliferating and non-proliferating lymphocytes, HU did not exert any significant effect. Thus, the effect of HU on T cell activation is not direct and seems to be mediated through its effect on T cell proliferation.

[Immunophenotype of progression to AIDS: deficiency, activation and dysfunction of CD4 and CD8 T-cells]. / Inmunofenotipo de progresión a sida: deficiencia, activación y disfunción de células T CD4 y CD8.

INTRODUCTION: One key piece of information required when deciding whether to initiate antiretroviral therapy is the risk of AIDS. The aim of this study was to better characterize the baseline immunophenotypic profile of patients with progression to AIDS. MATERIAL AND METHODS: A cross-sectional analysis of the distribution of functional subpopulations of CD4+ and CD8+ T-lymphocytes in 85 intravenous drug addicts with HIV infection. The values observed on patient enrolment in a prospective study were analyzed. Those patients who progressed and did not progress were compared to the HIV-negative controls. Lymphocyte subpopulations were studied by flow cytometry, including the markers: CD3, CD4, CD7, CD8, CD45RO, CD38, HLA-DR and CD25. RESULTS: The immunophenotypic profile that precedes progression to AIDS was mainly characterized by an increase in memory (CD45RO) activated cells and total activated CD4+ and CD8+ cells, and by an increase of T CD4+ cells that have loss expression of markers as receptor or the differentiation marker CD7 (CD7-). Patients not meeting laboratory criteria to initiate antiretroviral therapy (> 350 CD4+ T-cells and < 30,000 HIV-ARN-copies/ml) also showed increased levels of CD4+ and CD8+ activation subsets (CD4+CD38+DR+, CD8+CD38+). DISCUSSION: The fact that immunological activation may contribute to immunological and clinical deterioration of HIV-positive patients might be an additional factor which should be taken into account when deciding whether to initiate antiretroviral therapy.

Synthesis and evaluation of calystegine B2 analogues as glycosidase inhibitors.

A practical synthesis of polyhydroxylated 6-oxa-nor-tropanes incorporating the essential structural features of calystegine B(2) from 5-deoxy-5-thioureido and 5-ureido-L-idofuranose precursors is presented. The methodology relies on the ability of pseudoamide-type nitrogen atoms (thiourea, urea, and carbamate) to undergo nucleophilic addition to the masked aldehyde group of the monosaccharide. The generated hemiaminal functionality may further undergo in situ intramolecular glycosidation to give the bicyclic aminoacetal compounds, the whole process being favored by the anomeric effect. A series of derivatives bearing different substituents at nitrogen has been prepared and screened against several glycosidases in comparison with xylonojirimycin-type piperidine analogues. Interestingly, strong and highly specific inhibition of bovine liver beta-glucosidase was observed for 6-oxacalystegine B(2) analogues incorporating aromatic pseudoaglyconic groups. On the basis of these data, a 1-azasugar inhibition mode is proposed for this family of glycomimetics.

Carbohydrate-based receptors with multiple thiourea binding sites. Multipoint hydrogen bond recognition of dicarboxylates and monosaccharides.

The binding properties of multitopic sugar thiourea receptors toward dicarboxylate and monosaccharide guests have been examined taking glutarate and octyl beta-D-glucopyranoside as model ligands. For the anionic hydrogen bond acceptor, both the complex stoichiometry and the association constants (K(as)) were found to be strongly dependent on the relative disposition of recognition elements in the host. In contrast, for the glucoside guest a 1:1 stoichiometry was observed in all cases, the K(as) values being largely independent of the unbound state provided that geometrically equivalent supramolecular topologies can be achieved.

Carbohydrate-derived spiroketals. Stereoselective synthesis of di-D-fructose dianhydrides by boron trifluoride promoted glycosylation-spiroketalization of acetal precursors.

[reaction: see text] Di-D-fructose 1,2':2,1'-dianhydrides, dispiro-tricyclic disaccharides widely found in food materials, have been stereoselectively prepared in one-pot reaction from O-protected D-fructose 1,2-acetonide precursors by treatment with boron trifluoride diethyl etherate. The dimerization sequence involves (i) cleavage of the anomeric acetal linkage, (ii) autoglycosylation, and (iii) final spiroketalization, the stereochemical outcome being strongly dependent on the nature of the hydroxyl protecting groups.