Deri-vatives

Table 12.2 Epoxidation of olefins with bis(trimethylsilyl) peroxide (BTSP) catalyzed by high-valent oxorhenium deri-vatives> bl...

As has been described in Section 4.2.3, immobilized TADDOL-derivatives are particularly important catalytic species which can be applied to asymmetric synthesis in many ways. Seebach et al. developed a dendritic elongated TADDOL-deri-vative (32) that could be embedded in polystyrene by copolymerization (Scheme 4.18). Upon treatment with Ti(OiPr)4 the chiral polymeric diisopropoxy-Ti-TAD-... 

The diazo-stretching bands in 2-diazoimidazoles are found at lower wavenumbers (2105-2247 cm" ) than those observed in 4-diazo-deri-vatives (2140-2210 cm" ). 

Miscellaneous Preparations of Acetylenic Deri vatives 1. Halogen Compounds, Sulfinates, Sulfonates and Acetates All temperatures are internal, unless indicated otherwise... 

Diammino-zinc Chloride, [Zn(NII3)2]Cl2, is obtained by evaporation of the solution from which the tetrammino-deri vative is separated (see under). It may also be prepared by heating tetrammino-zinc chloride to a temperature of 149° C., or by dissolving zinc in an aqueous solution of ammonium chloride with the aid of metallic copper or silver, or by passing ammonia gas into a concentrated solution of zinc chloride in acetone.1... 

Tar oils. 0-860-0-900 80-145° Inactive More than 100 Complete Attacked with formation of nitro-deri-vatives... 

In the case of 1-halogeno 1-deoxy sugars, the competition of photobromination at C-5 or C-l depends on the halogen and its configuration. The regioselectivity of the reaction at C-l decreases from anomeric chlorides to fluorides, and the a-deri-vatives are less reactive or inert for the anomeric substitution. 

Schafer W, Ballschmiter K (1986), Chemosphere 15 755-763. Monobromo-polychloro-deri-vatives of benzene, biphenyl, dibenzofuran and dibenzodioxin formed in chemical-waste burning"... 

CHAPTER21 THE PREPARATION OF NITRO PARAF FI NS AND TH El R DERI VATIVES... 

De Bruyn u found that ozone adds to 9,10-dimethylanthracene to form 97, This product is obtained in almost quantitative yield when ozone is led into a solution of the anthracene deri vative in acetone. 

Hu, Sun and Scott described recently an efficient synthesis of some taxadiene deri-vatives . In their approach, alcohol (66) is treated with carbon disulphide followed by methyl iodide under standard conditions for the formation of xanthates, to afford the dithiocarbonate (67) in a process that presumably involved a Claisen rearrangement (Scheme 9). Interestingly, 67 undergoes smooth reaction with Bu3SnH to provide the reqnrred prodncts (68, 69... 

Trimethyl(trifluoromethyl)silanc reacts with the derivatives of four- and six valent sulfur-containing mobile halogen atoms to form the trifluoroniethyl deri vatives. Trifluoromethylation with trimethyl(trifluoromethyl)silane has also been used in the preparation of a trifluoro-methylatcd sugar derivative. 

The conveniently prepared pyruvated benzyl glycosides 12candl2c (Table 2) are first converted by a two-step sequences into the fluoride 47 and the TlPS-deri-vative 48, respectively. The latter are subsequently condensed, using the glyco-desilylation-protocol, to give the desired laminaritjiosides 49 in excellent yield. 

Since alkoxymethyleneiminium salts with nearly any substitution pattern are easy to prepare, this amidine synthesis has attained widespread application. Thus N-unsubstituted, IV-monosub-stituted and lV,A(-disubstituted alkoxymethyleneiminium salts (138) have been transformed to amidinium salts (137) by treatment with ammonia,primary and secondary amines and amine deri-vatives. ... 

The pure base is obtained by saponification of its diacetyl deri-vative with hydrochloric acid. The hydrochloride is a constituent... 

The last class of allylation reactions that are amenable to asymmetric catalysis employs allylboronate derivatives. Schaus reported that several chiral BINOL deri vatives catalyze the enantioselective asymmetric allylboration of acyl imines [97]. This reaction is most effective when 3,3 diphenyl BINOL acts as the catalyst and allyldii sopropoxyborane is the nucleophile. The allylation products are obtained in good yields (75 94%) and excellent enantiomeric excesses (>90% ee) for both aromatic and aliphatic imines (Table 1.13). 

Pregnane Series. Steroid allyl and propargyl enol ethers tindergo the Claisen rearrangement. - Surprisingly, cyanogen bromide reacts with 18-hydroxy-20-dimethylamino steroids to form the corresponding 18,20-epoxy deri-vatives. Additional work has been reported on the synthesis of l8-methyl steroids. ... 

The intestinal absorption of caproyl-deri-vatives of insulin was evaluated by measuring plasma glucose reduction after admin-... 

Acetylation of saccharide hydrazones (65) with acetic anhydride in pyridine affords per-O-acetylatcd derivatives (such as 66) with acyclic hydrazones and A-acetyl-O-acetyl derivatives with the cyclic ones. 5 "4 t 4,i63 jn [1C as, casC [lc [sjpi group attached to the aryl moiety is not acetylated, but the more basic NH group attached to the sugar moiety is acetylated. The 0-acetyl groups are split off by base more readily than the iV-acctyl groups.218 and methods for selective saponification have been devised. With acetyl chloride in A/, A-tli methyl aniline, the NH group attached to the aryl residue becomes acylated and acyclic hexose hydrazones give A-acetyl-penta-O-acctyl derivatives (64) 165 similarly, benzoylation with benzoyl chloride in pyridine affords W-benzoyl-0-bcnzoyl deri vatives (Scheme 15)219... 

Table 5.18 Analysis of the effect of the various property deri vatives on and yxxzzof pyrrole (all in a.u.) ...

Chromatography Nimura et al. [107] separated the deri vatives of norepinephrine and dopamine using a reversed phase HPLC column wih pH 6.5 phosphate buffer/ methanol. The eluate was monitored using a fluorescent detector with excitation and emission wavelengths of 340 and 450 nm, respectively. 

Photoaffinity labels are an efficient tool for identification of inhibitor binding proteins in the photosynthetic electron transport chain. [ H]Azido-dinoseb, an azido-deri-vative of the phenolic herbicide dinoseb, was synthesized almost a decade ago and was shown to bind primarily to a 41 kDa protein (1,2). Contrary, labeling with azido-deri-vates of diuron-type herbicides revealed that these herbicides bind to a 32 kDa protein, which has now been recognized as the D-1 protein of the photosystem II reaction center core complex (see references in (3)). Tyrosine residues in positions 237 and 254 of the D-1 sequence were demonstrated to be the primary target of [ CJazido-monuron (3). The phenolic herbicide [ I]azido-ioxynil also labels predominantly the D-1 protein in position of Val249 and only in trace amounts a 41 kDa protein (4). 

Besides cyclodextrin derivatives, other mixed special selectivity stationary phases also had synergistic effects in the separation of isomers. Those reported include dibenzo-18-crown-6 -I- MPBHpB, dibenzo-18-crown-6 and resorcarene derivative,MPBHpB + resorcarene deri-vative, and 25,27-dibutoxy-5,ll,17,23-tetra-terf-butyl-26,... 

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