Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time, and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes, vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge, it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Synthesis Of Indolizidine And Pyrrolizidine Alkaloids By The [2+2] Cycloaddition Of Endocyclic Enecarbamates To Alkyl Ketenes

The total syntheses of the necine base (±)-platynecine and of a new indolizidine were accomplished. Both syntheses feature a [2+2] cycloaddition of a common endocyclic enecarbamate with alkylketenes in a new and concise strategy for the construction of pyrrolizidine and indolizidine skeleta. These syntheses were carried out in four steps in good overall yields. © 1995.362951095112Michael, (1994) Nat. Prod. Rep., pp. 17-39. , Indolizidine alkaloids:Michael, (1994) Nat. Prod. Rep., pp. 639-657. , and references cited thereinRobins, (1994) Nat. Prod. Rep., pp. 613-619. , Pyrrolizidine alkaloids:, and references thereinOlden, Breton, Grzegorzewski, Yasuda, Gause, Oredipe, Newton, White, (1991) Pharmac. Ther., 50, p. 285Suffiness, Cordell, (1985) The Alkaloids: Chemistry and Pharmacology, 25. , A. Brossi, Acad. Press, New York, chapter 1Faria, Matos, Correia, (1993) Tetrahedron Lett., 34, pp. 27-30At first we considered an ionic-stepwise mechanism the major operating mechanism for the [2+2] cycloaddition reaction of endocyclic enecarbamates and enamides to ketenes.4 This assumption was based on the results obtained by Huisgen for the [2+2] cycloaddition of enamines to ketenes (Otto, P,Feiller, L. A.Huisgen, R. Angew. Chem., Int. Ed. Engl. 1968, 7, 737–738.). However, attempts to perform [2+2] cycloaddition of endocyclic enecarbamates to alkylketenes in more polar solvents (CH2Cl2, THF) led only to decomposition. The results obtained so far in our studies with endocyclic enecarbamates indicates these as activated double bonds, but still retaining some of the enamines characteristic reactivity. Similar observation was made previously by Lenz for enamides (Lenz, G. R. Synthesis 1978, 489–518.)Krow, (1993) Org. React., 43, pp. 251-798. , For a comprehensive review on the Baeyer-Villiger reaction see:, see alsoKrow, (1991) Comprehensive Organic Synthesis, 7, pp. 671-688. , S.V. Ley, Pergamon Press, Oxford, For examples of the influence of conformational factors on the regioselectivity of Baeyer-Villiger reactions in α-substituted cyclohexanones see:Chida, Tobe, Ogawa, (1994) Tetrahedron Lett., 39, pp. 7249-7252Beauhaire, Ducrot, Malosse, Rochat, Ndiege, Otieno, (1995) Tetrahedron Lett., 36, pp. 1043-1046Ohmiya, Kubo, Otomasu, Saito, Murakoshi, (1990) Heterocycles, 30, pp. 537-542. , For a recent synthesis of tashiromine see:Paulvannan, Stille, (1994) J. Org. Chem., 59, pp. 1613-1620All new compounds gave satisfactory spectroscopic data. Representative data for some new compounds: 9HCl salt, sublimes above 200 °C: 1H NMR (300 MHz,D2O) δ: 4.90 (m, 1H), 4.45 (t,1H), 3.70 (t, 1H), 3.45 (dd, 1H), 3.40-3.10 (m, 3H), 2.35 (dd, 1H), 2.30-2.00 (m, 2H), 1.90-1.60 (m, 3H)13 C NMR (75 MHz, D2O) δ: 178.8, 74.7, 59.5, 51.2, 46.7, 46.4, 27.2, 22.7, 11.0IR (KBr): 2467-2411, 1760 cm−1MS (m/z): 176 (M+), 166, 149, 129, 97, 82, 69 (100%)10, 1 H NMR (300 MHz, CDCl3) δ: 4.19 (s, 1H), 3.90-3.50 (m, 5H), 3.20-3.00 (m, 2H), 2.35 (m, 1H), 2.20-1.35 (m, 8H)13 C NMR (75 MHz, CDCl3) δ: 69.2, 65.7, 63.3, 54.1, 54.0, 41.9, 31.8, 24.8, 19.5IR (neat): 3329, 2937, 2794 cm−1MS (m/z) 171(M+), 170, 140, 127, 114, 96 (100%), 68, 41Viscontini, Buzek, �ber Pyrrolizidinchemie. 11. Mitteilung [1]. Totalsynthese von (�)-Platynecin (1972) Helvetica Chimica Acta, 55, pp. 670-674Rüeger, Benn, The Enantioselective Synthesis of (+)-Retronecine, (—)-Platynecine, and (+)-Croalbinecine and Its C-1 Epimer (1983) HETEROCYCLES, 20, pp. 1331-1334Niwa, Kuroda, Yamada, A convenient synthesis of (.+-.)-retronecine. (1983) Chemistry Letters, pp. 125-12

Spatial variability of microbial biomass and organic matter labile pools in a haplic planosol soil

The objective of this work was to study the spatial variability of soil microbial biomass (SMB) and labile soil organic matter pools (labile SOM), under different management systems and plant cover. The experiment was conducted in a Haplic Planosol soil on an Integrated Agroecological Production System (SIPA), in Seropédica, Rio de Janeiro. The evaluated management systems were: alley cropping, pasture, and bush garden, the late one was used as reference area. Three grids of regular spacing of 2.5 x 2.5 meters were used for sampling, consisting of 25 georeferenced points each, where soil samples were taken at 0-10 cm depth. The following labile constituents of soil organic matter were determined: free light fraction (FLF), water soluble C and N, C and N of SMB (SMB-C and SMB-N), and glomalin content. The textural fractions (sand, silt, and clay), pH in water, and chemical attributes (organic C, total N, Ca, Mg, Al, P, K, and CEC-cation exchange capacity) were also determined. The areas of alley cropping and pasture showed spatial dependence to the attributes of SOM. The occurrence of high spatial dependence for the attributes associated to microbial biomass in the alley cropping system (C, FLF, SMB-N and respiration), probably was due to external factors related to management, such as: intensive rotational cropping system, diversity of crops and different inputs of organic matter to soil such as pruning material and organic compost