Cyclodextrin partially methylated

For long chain olefins, the hydroformylation generally proceeds slowly and with low selectivity in two-phase systems due to their poor solubility in water. Monflier et al. recently reported a conversion of up to 100% and a regioselectivity of up to 95% for the Rh-catalyzed hydroformylation of dec-l-ene in water, free of organic solvent, in the presence of partially methylated 6-cyclodextrins (Eq. 3.42).173... 

Ou, D. Ueda, H. Nagase, H. Endo, T. Nagai, T. Some pharmaceutical properties of 2,3,6-partially methylated-P-cyclodextrin and its solubilizing and stabilizing abihties. Drug Dev. Ind. Pharm. 1994, 20 (12), 2005-2016. 

Tsuchiyama, Y. Sato, M. Yagi, Y. Ishikura, T. Partially Methylated Cyclodextrins and Process for the Producing the Same. US Patent 4,746,734, 1988. 

Considerable progress has been made with the study of substituted derivatives. The L-histidyl-L-histidyl derivative (32), which is a potential enzyme mimic with two recognition sites, has been made from a 6-deoxy-6-iodo-/3-cyclodextrin. A somewhat related pair of substances, 6-N-(N -formyl- )- and L-phenylalanyl)-6-amino-6-deoxy-(3-cyclodextrin, were made from the 6-amino compound and their inclusion behaviour was studied. In similar work the 6-monoazide was partially methylated and reduced, and the amino product was coupled with both enantiomers of N-protected phenylalanine. Other workers have reported the fully O-methylated 6-azido-6-deoxy p-compound. ... 

Cyclodextrins, toroidal molecules composed of 6, 7 and 8 D-glucose units, are now commercially available at reasonable cost. They form inclusion compounds with a variety of molecules and often differentially include sulfoxide enantiomers29,30. This property has been used to partially resolve some benzyl alkyl, phenyl alkyl and p-tolyl alkyl sulfoxides. The enantiomeric purities after one inclusion process ranged from 1.1 % for t-butyl p-tolyl sulfoxide to 14.5% for benzyl r-butyl sulfoxide. Repeating the process on methyl p-tolyl sulfoxide (10) increased its enantiomeric purity from 8.1% to 11.4% four recrystallizations raised the value to 71.5%. The use of cyclodextrins in asymmetric oxidations is discussed in Section II.C.l and in the resolution of sulfmate esters in Section II.B.l. 

It is well known that spontaneous resolution of a racemate may occur upon crystallization if a chiral molecule crystallizes as a conglomerate. With regard to sulphoxides, this phenomenon was observed for the first time in the case of methyl p-tolyl sulphoxide269. The optical rotation of a partially resolved sulphoxide (via /J-cyclodextrin inclusion complexes) was found to increase from [a]589 = + 11.5° (e.e. 8.1%) to [a]589 = +100.8 (e.e. 71.5%) after four fractional crystallizations from light petroleum ether. Later on, few optically active ketosulphoxides of low optical purity were converted into the pure enantiomers by fractional crystallization from ethyl ether-hexane270. This resolution by crystallization was also successful for racemic benzyl p-tolyl sulphoxide and t-butyl phenyl sulphoxide271. 

A Amini, N Merclin, S Bastami, D Westerlund. Determination of association constants between enantiomers of orciprenaline and methyl-/3-cyclodextrin as chiral selector by capillary zone electrophoresis using a partial filling technique. Electrophoresis 20 180-188, 1999. 

Many CDs have been successfully used to solubilize insoluble drugs, here are a partial list of CD derivatives reported in the literature fflFCD, SBE-ft-CDs, randomly methylated-P-cyclodextrin (RM-p-CD), 2,3,6-partially methylat flcyclodextrin (PM-ft-CD), glucosyl-ft-CD (G1-P-CD), maltosyl-p-cyclodextrin (G2- -CD), hydroxyethyl-p-cyclodextrin (He-p-CD), diethyl-P-cyclodextrin (DE-p-CD)P-carboxymethyl-Qethyl- -cyclodextrin (CME-p-CD), and (2,6-oG>-methyl)-p-cyclodextrin (DOM-p-CD). 

Photoformylation (the photo-Riemer-Tiemann reaction) of phenols (phenol, 2-methyl, 3-methyl, 4-methyl, 4-chloro, 4-bromo, 4-nitro and 4-phenyl phenol) has also been studied by irradiation in chloroform with KOH and pyridine. The yields reported are variable but formylation is reported only to occur in the 2-position ° °. This process involves the addition to phenol of radicals produced from chloroform. An electron transfer mechanism (transfer from excited state phenol to chloroform) is thought to be involved. The radical ion pair eliminates HCl and combination affords the products 232-234 (Scheme 26). The principal product is the ether and this undergoes partial conversion to the formate. The other products formed in low yield are the aldehydes . In another application of the photo-Riemer-Tiemann reaction, this time in cyclodextrin, the phenols can be converted into 4-hydroxybenzaldehydes with high selectivity . ... 

Cyclodextrins are the most used host compounds so far. Native cyclodextrins are effective inverse phase-transfer catalysts for the deoxygenation of allylic alcohols [3], epoxidation [4], oxidation [5], or hydrosilylation [6] of olefins, reduction of a,y9-unsaturated acids [7], a-keto ester [8], conjugated dienes [9] or aryl alkyl ketones [10]. Interestingly, chemically modified cyclodextrins like the partially O-methylated y0-cyclodextrin (RAME-y9-CD) show a better catalytic activity than native cyclodextrins in numerous reactions such as the Wacker oxidation [11], hydrogenation of... 

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