C9 ethers

The natural cinchona alkaloids were shown also to catalyze conjugate addition followed by an oxa-nudeophUic rearrangement in the reaction of 2-(l-hydro3 y-3-arylaUylidenejmalonates with p,y-imsaturated a-ketoesters (Scheme 6.5) [20]. Alkaloid 1 gave the best yields and enantioselectivities compared to other natural cinchona alkaloids and C9 ethers derivatives while a C9 phenyl substituted derivative of quinine appeared to be imreactive. 

Catalysis with C9 Ethers of Natural Cinchona Aikaioids... 

The simple C9 ethers derived from the natural cinchona alkaloids are infrequently applied in organocatalysis. A relatively recent example concerns an asymmetric cyclopropanation reaction with the C9 O-methyl derivatives of 1 and 4, respectively (Scheme 6.13) [35]. The functionalized cyclopropanes were obtained in excellent diastereo- and enantioselectivity as well as in high yields. 

The importance of an -OH group at the C6 position for an organocatalytic reaction was noted by Deng and coworkers in a series of studies of C9 ether derivatives of cupreine and cupreidine [34]. Based on the observation that the C9 0-benzyl and O-phenanthryl ether derivatives (10 and 11, respectively. Figure 6.5) gave similar results for the conjugate addition of carbon nucleophiles to nitroalkenes as obtained with 3 (Scheme 6.18) [34], a transition state model was proposed for this reaction. 

Me3SiNEt2- Trimethylsilyldiethylamine selectively silylates equatorial hydroxyl groups in quantitative yield (4-10 h, 25°). The report indicated no reaction at axial hydroxyl groups. In the prostaglandin series the order of reactivity of trimethylsilyldiethylamine is Cii > Ci5 C9 (no reaction). These trimethylsilyl ethers are readily hydrolyzed in aqueous methanol containing a trace of acetic acid. The reagent is also useful for the silylation of amino-acids. ... 

Q =6-Methoxy-quinolyl in formulae (p, 449). Quinidine (0-5) Quinine (I-O) Dihydro-quinidine (0-5-1-0) Dihydroquinine (1-2) opoQuinidine methyl ether (1-0) a-isoQuinine (0-02). j8-i.9oQuinine (0-C9) a-isoQuinidine (0-0C5) 8-isoQuinidine (01) y-isoQuinidine (inactive) a-Hydroxydi- hydroquinine (0-54) Niquidine (1-45) isoNiquidine (1-05) Niquine (0-86)... 

With the iodine atom in its proper place, provisions for construction of the C9-C10 bond by an aldol reaction could be made (see Scheme 44). To this end, oxidative cleavage of the para-methoxy-benzyl ether in 181 with 2,3-dichloro-5,6-dicyano-l,4-benzoqui-none (DDQ) in CH2CI2-H2O furnishes a primary alcohol that can... 

Compounds where the Cl hydroxyl group is linked to the C2 position by a cyclic ether link, with a range of different groups in the C9 position, were prepared by Reggio et al. [216]. These compounds showed only modest CB2 selectivity. Compound (341) was the most potent and selective with a binding affinity (A)) of 5.8 nM at CB2 and 26nM at CBi. 

Diaminourea, c9 Diamylamine, d737 Diamyl ether, d738 Diamyl ketone, ull Diazirine, d63... 

C4-C5 bond formation and between C9 and CIO. In both cases, the addition of silyl enol ether 2 to furfural was achieved with the T0I-BINAP-CUF2. For the synthesis of the C1-C7 segment the S-catalyst was used and the J -catalyst furnished segment 27 (Scheme 11). 

The lignin (50 g) was dissolved in a mixture of dioxane (500 ml) and methanol (1,000 ml), and ozonized at 0°C with an oxygen flow rate of 0.5 ml/min and ozone concentration of 3% as shown in Figure 3. After treatment with ozone, the solution was treated with an excess amount of ether, and the insoluble fraction was filtered off, followed by drying under vacuum. Three samples (No. 1, No. 2, and No. 3) differed in the extent of ozone treatment as shown in Table I. The molar equivalents were based on the ratio of ozone to each phenylpropane (C9) unit. The yield of each sample is also shown in Table I. 

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