Antarctica products

Faure G, Lord BK (1990) Oxygen and carbon isotope compositions of calcite in carbonate concretions in the Beacon rocks of Antarctica Products of the Gondwana ice sheet. In Ulbrich H, Rocha Campos AC (eds) Gondwana Seven Proceedings. Institute de Geociencias, Universidade de Sao Paulo, Brazil, pp 303-315... 

Rice is grown in more than 100 countries and on every continent except Antarctica. In the world economy rice is an extremely important food, second only to wheat in total world production, and its yield per hectare exceeds that of wheat (57). Rice is the main staple food for more than half of the world s population and it accounts for one-third to one-half of the daily caloric intake in many Asian countries. It is also the major source of protein for the masses of Asian people. In many African and South American countries rice is rapidly becoming the staple food for much of the population. 

Every continent, except Antarctica, grows com 40% of the present world crop is produced in the United States. In the 1987—1988 crop year, 12 states (Iowa, HI., Nebr., Minn., Ind., Ohio, Wis., Mo., S. Dak., Mich., Kans., and Tex. in order of production) produced 157.5 million metric tons (6.2 biUion bushels) that was 88% of the United States and 36% of the world s crop (66). Yield is influenced by many factors, including climate, pest control, planting density, and fertilization. Yield in the United States has increased from about 1.5 metric tons /hectare in the 1930s to about 7.5 metric tons /hectare. In 1985, a test plot produced 23.2 metric tons /hectare and yields approaching 40 metric tons /hectare are considered possible com is the most productive of the principal food crops. 

The Montreal Protocol of July 1987 resulted in an international treaty in which the industrialized nations agreed to halt the production of most ozone-destroying chlorofluorocarbons by the year 2000. This deadline was hastily changed to 1996, in February 1992, after a U.S. National Aeronautics and Space Administration (NASA) satellite and high-altitude sampling aircraft found levels of chlorine monoxide over North America that were 5i % greater than that measured over Antarctica. 

Coal is the most abundant and most economical fossil fuel resource in the world. Proven coal reseiwes exceed 1 trillion tons, and indicated reserves are estimated at 24 trillion tons. Coal is found in eveiy continent of the world, including Antarctica, although the largest quantities of coal are in the Northern Hemisphere. Coal is mined in some sixty countries in nineteen coal basins around the world, but more than 57 percent of the world s total recoverable reserves are estimated to be in the United States, and China, which together account for more than two-thirds of the world s coal production. 

A month-long study of the effects of ultraviolet radiation (UV) on phytoplankton and ice-algae collected from Arthur Harbor, Anvers Island, Antarctica, was carried out during November-December 1987. The parameters studied included primary production rates, photosynthetic... 

Effect of UV on Productivity of the Southern Ocean. Has ozone depletion over Antarctica affected the productivity of the Southern Ocean There is no easy answer. First, one has to take into account the fact that the drastic decrease of ozone over Antarctica has been reported as recently as 1976, a relatively short time in the evolution of the organisms to develop mechanisms to cope with elevated UV. One of the most vexing problems in studying the effects of UV radiation on productivity, is a dearth of historical data on the level of UV. Without these baselines, normal fluctuations could easily be interpreted as decline in productivity. Second, there is a host of biotic and abiotic factors that play significant roles in governing the productivity of the Southern Ocean (40). Ultraviolet radiation is but one more complicating factor to be considered in an already stressful environment. 

Fluxes of continental dust preserved in ice cores of Greenland and Antarctica suggest a 30-fold increase in dust flux during the last Glacial Maximum. Dramatic increases in new biological production in the HNLC regions may have resulted, resulting in the draw-down of atmospheric CO2 (Martin, 1990). 

For desymmetrization of diesters 3 via their hydrolysis in water, pig Hver esterase [12], o -chymotrypsin [12, 13a], and Candida antarctica Hpase (CAL-B) [14] were successfully used. However, further studies showed that respective anhydrides 5 can be used as substrates for enzyme-catalyzed desymmetrization in organic solvents [15]. The desired monoesters 4 were obtained in high yield in this way, using immobilized enzymes Novozym 435 or Chirazyme L-2 (Scheme 5.3). After the reaction, enzymes were filtered off, organic solvents were evaporated, and the crude products were crystalHzed. This was a much simpler experimental procedure in which control of the reaction progress was not necessary, and aU problems associated with extraction of products from aqueous phase and their further purification were omitted [15]. 

The DKR of secondary alcohols can be efficiently performed via enzymatic acylation coupled with simultaneous racemization of the substrates. This method was first used by BackvaU for the resolution of 1-phenylethanol and 1-indanol [38]. Racemization of substrate 18 by a mthenium catalyst (Scheme 5.11) was combined with transesterification using various acyl donors and catalyzed by C.antarctica B Hpase. From aU the acyl donors studied, 4-chlorophenyl acetate was found to be the best. The desired product 19 was obtained in 80% yield and over 99% ee. 

The chlorine atoms in the upper atmosphere come from the breakdown of CF2 CI2 and other similar chlorofluorocarbons (CFCs), known commercially as Freons. Production of these compounds was more than one million tons in 1988, largely for use in relrigerators and air conditioners. Once released into the atmosphere, CFCs diffuse slowly upward in the atmosphere until they reach the ozone layer. There, ultraviolet light Irom the sun splits off chlorine atoms. These react with ozone, with dramatic results. Annual ozone decreases have exceeded 50% above Antarctica. The background photo shows the Antarctic hole (red-violet) on September 24, 2003. 

Stierle, D. B. and Sims, J. J. 1979. Marine natural products—V. Polyhalogenated cychc monoter-penes from the red alga Plocamium cartilagineum of Antarctica. Tetrahedron 35 1261-1265. 

Sarin MM, Kim G, Church TM (1999) °Po and °Pb in the South-equatorial Atlantic distribution and disequilibrium in the upper 500 m. Deep-Sea Res II 46 907-917 Schmidt S, Andersen V, Belviso S, Marty JC (2002) Strong seasonahty in particle dynamics of northwestern Mediterranean surface waters as revealed by " Th/ U. Deep-Sea Res 149 1507-1518 Shimmield GB, Ritchie GD, Fileman TW (1995) The impact of marginal ice zone processes on the distribution of °Pb, °Po and " Th and implications for new production in the Bellinghausen Sea, Antarctica. Deep-Sea Res II 42 1313-1335... 

An interesting example of biocatalysis and chemical catalysis is the synthesis of a derivative of y-aminobutyric acid (GABA) that is an inhibitor for the treatment of neuropathic pain and epilepsy (Scheme 10.4). The key intermediate is a racemic mixture of cis- and trons-diastereoisomer esters obtained by a hydrogenation following a Horner-Emmons reaction. The enzymatic hydrolysis of both diaste-reoisomers, catalyzed by Candida antarctica lipase type B (CALB), yields the corresponding acid intermediate of the GABA derivative. It is of note that both cis- and trans-diastereoisomers of the desired enantiomer of the acid intermediate can be converted into the final product in the downstream chemistry [10]. 

Biphasic systems consisting of ionic liquids and supercritical CO2 showed dramatic enhancement in the operational stability of both free and immobilized Candida antarctica lipase B (CALB) in the catalyzed kinetic resolution of rac- -phenylethanol with vinyl propionate at 10 MPa and temperatures between 120 and 150°C (Scheme 30) 275). Hydrophobic ionic liquids, [EMIM]Tf2N or [BMIM]Tf2N, were shown to be essential for the stability of the enzyme in the biotransformation. Notwithstanding the extreme conditions, both the free and isolated enzymes were able specifically to catalyze the synthesis of (J )-l-phenylethyl propionate. The maximum enantiomeric excess needed for satisfactory product purity (ee >99.9%) was maintained. The (S)-l-phenylethanol reactant was not esterified. The authors suggested that the ionic liquids provide protection against enzyme denaturation by CO2 and heat. When the free enzyme was used, [EMIM]Tf2N appeared to be the best ionic liquid to protect the enzyme, which... 

Hansen, T.V., Waagen, V., Partali, V., Anthonsen, H.W. and Anthonsen, T. (1995) Cosolvent enhancement of enantioselectivity in lipase-catalysed hydrolysis of racemic esters. A process for production of homochiral C-3 building blocks using lipase B from Candida antarctica. Tetrahedron Asymmetry, 6, 499-504. 

Lundhaug, K., Overbeeke, P., Jongejan, J. and Anthonsen, T. (1998) Organic co-solvents restore the inherently high enantiomeric ratio of lipase B from Candida antarctica in hydrolytic resolution by relieving the enatiospecrfic inhibition of product alcohol. 

The oxidation of dimethyl sulfide (DMS) to dimethyl sulfoxide (DMSO) and the subsequent oxidation of the latter to methanesulfonic acid (MSA) have been observed in field studies. For example, one study in Antarctica which focused on the chemistry of dimethyl sulfide (Berresheim and Eisele, 1998) measured not only DMS but also a variety of its oxidation products, including DMSO, MSA, and dimethyl sulfone (Berresheim et al., 1998). The measured concentrations of DMSO were in agreement with model results if 80-100% of the OH + DMS reaction gave DMSO as discussed earlier, the addition channel that leads to DMSO becomes relatively more important at the lower temperatures found in Antarctica. Furthermore, the... 

Through a variety of studies, it is now generally accepted that the observed losses are associated with chlorine derived from CFCs and that heterogeneous chemistry on polar stratospheric clouds plays a major role. The chemistry in this region is the result of the unique meteorology. As described in detail by Schoeberl and Hartmann (1991) and Schoeberl et al. (1992), a polar vortex develops in the stratosphere during the winter over Antarctica. The air in this vortex remains relatively isolated from the rest of the stratosphere, allowing photochemically active products to build up... 

Nozaki et al. [23] characterised the production of (+)-mesifuran [2,5-di-methyl-4-methoxy-3(2H)-furanone], an important flavour compound in arctic bramble, but which also occurs in strawberry and pineapple. After lipase-catalysed (Candida antarctica) enantioface-differentiating hydrolysis of the enol acetate, the pure optically active (+)-mesifuran could be obtained. 

An interesting case is the resolution of a heterohelicenediol. The very bulky racemic substrate roc-15 is resolved by lipase-catalyzed acylation with vinyl acetate in dichloromethane. Oddly enough, Candida antarctica lipase (CAL) and Pseudomonas cepacia lipase (PCL) display opposite enantiopreferences [54]. In Scheme 4.13, only the remaining substrates are shown and not the other products, the mono- and diacetates. 

The rather complex furylvinylcarbinol derivative 76 shown in Scheme 4.28 was required in enantiopure form as a key intermediate in the synthesis of the natural product cneorin. The carbinol moiety is heavily substituted with sterically demanding groups. Therefore attempts to resolve the furylvinylcarbinol with CALB or lipase PS-II led to very slow reactions. However, the rarely used enzyme Candida antarctica lipase A (CALA), which is known to act on sterically hindered substrates offers an alternative. Thus acylation of the furylvinylcarbinol 76 with 2,2,2-trifluoroethyl butanoate catalyzed by CALA (immobilized on celite with sucrose at pH 7.9) furnished the enantiomerically enriched propanoate of S-76 and R-76 (Scheme 4.28) [90]. Small-scale experiments gave E > 300. 

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