Reaction sporadic

In vivo, one of the main groups of carotenoids are the snlfates of eritoxanthin sulfate and of the caloxanthin sulfates. The sulfates of carotenoids are not associated with pigment-protein complexes, for example, they are neither part of the fight harvesting complexes nor of the reaction centers. In nonphotosynthetic bacteria, carotenoids appear sporadically and when present, they have unique characteristics. Some Staphylococci accumulate C30 carotenoids, flavobacteria C45 and C50, while some mycobacteria accumulate C40 carotenoid glycosides. ... 

The degradation of alkynes has been the subject of sporadic interest during many years, and the pathway has been clearly delineated. It is quite distinct from those used for alkanes and alkenes, and is a reflection of the enhanced nucleophilic character of the alkyne C C bond. The initial step is hydration of the triple bond followed by ketonization of the initially formed enol. This reaction operates during the degradation of acetylene itself (de Bont and Peck 1980), acetylene carboxylic acids (Yamada and Jakoby 1959), and more complex alkynes (Figure 7.18) (Van den Tweel and de Bont 1985). It is also appropriate to note that the degradation of acetylene by anaerobic bacteria proceeds by the same pathway (Schink 1985b). 

More particularly, a serious breakthrough was achieved in the methods of electrochemical calorimetty. Initial conclusions as to anomalous heat evolution during the electrolysis of solutions prepared with heavy water were caused by an incorrect formulation of control experiments in light water. In fact, none of the communications confirming anomalous heat evolution have been free of procedural errors, so that one cannot even discuss a sporadic observation of this effect. In contrast to all other experimental manifestations, heat evolution is indicative of any possible nuclear transformation, which implies that in its absence, neither reaction (33.4.1) nor reaction (33.4.2) can be suggested to occur. 

Palladium hydride is a unique model system for fundamental studies of electrochemical intercalation. It is precisely in work on cold fusion that a balanced materials science approach based on the concepts of crystal chemistry, crystallography, and solid-state chemistry was developed in order to characterize the intercalation products. Very striking examples were obtained in attempts to understand the nature of the sporadic manifestations of nuclear reactions, true or imaginary. In the case of palladium, the elfects of intercalation on the state of grain boundaries, the orientation of the crystals, reversible and irreversible deformations of the lattice, and the like have been demonstrated. 

Other sporadic examples of [2 + 2] cycloadditions of olefins on the exo double bond of structurally more complex MCPs, such as methylenecyclo-propenes, allylidene-, and alkenylidenecyclopropanes, have been reported. Thus, dicyclopropylideneethane (2) reacted with TCNE (131) to give the [2 + 2] adduct 164 as a minor product, together with the prevalent [4 + 2] adduct 163 (Scheme 76) [39], The same reaction in a different solvent had been previously reported to furnish exclusively the Diels-Alder product (see Sect. 2.1.2) [5]. 

It would be unfair to leave unmentioned other host molecules, capable of promoting catalytic reactions in aqueous media. Appropriately modified caHxarenes and crown ethers have been used sporadically for such purposes. Although the potential of very specific applications of these host molecules cannot be denied, from the practical view of availability and price, however, these are a far cry behind cyclodextrins. 

Because of their many side reactions, sulfonyl isocyanates, and especially the highly reactive chlorosulfonyl isocyanates, have been only sporadically employed (21HCA861). 

Scheme 6 Fructose can be transformed into 5-hydroxymethyl furfural (HMF) via acid-catalyzed dehydration. Solid acid catalysts applied to facilitate the reaction are zeolites, ion-exchange resins and solid inorganic phosphates. With sporadic success, notably with inorganic phosphates, other carbohydrate sources such as inulin can also be transformed into HMF.

In addition to solid-state reactions, other processing techniques of such ceramics have also been sporadically investigated, and have generally been the subject of new patents in the biomedical field. 

After the sulfation of alcohols and phenols was reported to proceed efficiently with DCC/ H2S04, 75 76 Wieland et al. 81 applied this procedure for the sulfation of the tyrosine residue in D-Tyr6-a//-D-retro-antamanide. This contains no reactive group in addition to the phenolic group, and the desired product was obtained in satisfactory yields. Despite these promising initial results, this type of sulfation reaction has been adopted only sporadically, e.g. for sulfation of the CCK-8 derivative Boc-Asp(OtBu)-Tyr-Met-Gly-Trp(For)-Met-Asp-(OtBu)-Phe-NH2 with 70% yield1 2 or for the preparation of an intermediate fragment in the synthesis of CCK-related peptides (Scheme 3). 83 ... 

Only sporadic use was made of the reaction until the late 1950 s, when Zhdanov and coworkers undertook the synthesis of numerous... 

Ammonium fluoride itself is not widely used, however, sporadic reference to it exists.187 Tetramethylammonium fluoride gives very good yields of the fluoro derivative 2 on reaction with l,6-anhydro-3,4-di-0-benzyl-2-0-(trifluoromethanesulfonyl)-/l-D-mannopyranose (1) in... 

The initial interest in deuterium labeling for biological experiments, which was begun in the 1930 s, soon faded in favor of the use of radioactive isotopes. Up until about ten years ago, deuterium labeling was used sporadically, mainly for reaction mechanism studies. An important upsurge in the use... 

Barton and coworkers exploited this strategy in the preparation of overcrowded ethylenes456 usually the desulfurization of a thiirane is accomplished by one equivalent of tertiary phosphine, mainly triphenylphosphine. However, spontaneous loss of sulfur from thiiranes substituted by aryl or halogen has sporadically been reported. Huisgen has reviewed this subject455 and performed many kinetic studies. He found that the desulfurization step can be accomplished by catalytic thiolates and also by thiobenzophenone or other thioketones, although in this case the reaction is slower (equation 131). 

In one large study, some adverse reactions in treated women were due to its ovulatory effects and others were direct reactions to the substance itself (2). The most common problem was ovarian enlargement (14%), followed by hot flushes (11%), abdominal and pelvic discomfort (7.0%), and nausea and vomiting (2.1%). Incidental symptoms were breast discomfort, vaginal changes, psychological symptoms, headache, heavier menses, and increased urinary frequency. Sporadic case-reports on clomiphene in the literature relate to fetal ovarian dysplasia or maternal psychosis (SEDA-7, 391), either of which may have been coincidental. However, it must be borne in mind that the substance is related structurally to tripar-anol, an obsolete drug that produced a series of disastrous adverse effects some 40 years ago. 

A 6-year-old boy developed recurrent generalized urticaria 1 year after he started to use human Mixtard insulin (132). The rash started 10 minutes after injections in the arms, thighs, and buttocks, at sites where earlier injections had been given, and disappeared within 12 hours. When he was changed to insulin lispro he had three urticarial reactions in the first 2 weeks and then sporadically. The reactions were treated with chlorphenamine for 2 years. 

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