10-phorsulfonic acid

The endothiopeptide amides have been converted into the corresponding 4H-l,3-thiazol-5-ones or 4/f-l,3-thiazol-5-imines in the presence of ( )- 10-cam-phorsulfonic acid (CSA) (Scheme 22).44 46... 

Racemic colchiceine was obtained by Corrodi and Hardegger by a base-catalyzed equilibration of the Schiff base obtained by reacting deacetyl-colchiceine with benzaldehyde (34). Aldimine-ketimine isomerization was found to be the mechanism by which the racemization had occurred (35). The optical resolution of deacetylcolchiceine was accomplished with cam-phorsulfonic acids, affording, after O-methylation with diazomethane, separation of the enolate isomers and after N-acetylation, unnatural (+)-and natural (-)- colchicine (Fig. 1). Racemization of colchicine in refluxing acetic anhydride followed by mild hydrolysis of the intermediate triacetate represents a much improved method of preparing ( )-colchicine (36). The Blade-Font procedure was later extended to the preparation of ( )-3-demethylcolchicine and other racemic analogs (5). 

SCHEME 14.9 Synthesis of lipid A from Helicobacter pylori. Alloc, allyloxycarbonyl CbzOBt, l-(benzyloxycarbonyl)benzotriazole CPME, cyclopentylmethyl etliel CSA, cam-phorsulfonic acid DMDO, dimethyldioxirane MNBA, 2-methyl-6-nitrobenzoic anhydride PMB, />-methoxybenzyl. 

Preparative Methods enantiomerically pure BINAP is obtained by resolution of the racemic dioxide, BINAPO, with cam-phorsulfonic acid or 2,3-di-O-benzoyltartaric acid followed by deoxygenation with Trichlorosilane in the presence of Trieth-ylamine ... 

DL-2-Thio-1 -phenyl-imidazolidine 1,2-Oibromoethane d-10-Cam phorsulfonic acid... 

Greico and Kaufman used a similar strategy, this time involving the Diels-Alder reaction of 3-vinylindole with an appropriately tethered imine, to construct the pentacyclic ebumamonine structure in a very efficient manner [108] (Scheme 65). At first attempt, the thermal Diels-Alder reaction of imine 307 in 1,2-dichlorobenzene at 180°C afforded the cycloadduct 308 in only 32% yield, and without the formation of ebumamonine (309). Next, cycloadditions under acidic conditions were examined. The optimal conditions were found to involve conducting the reaction at 5 M lithium perchlorate-diethyl ether with 0.1 equivalent of cam-phorsulfonic acid, thus affording the Diels-Alder product 308 in 96% yield. 

MBH adduct 825, obtained from A-Boc-a-amino aldehydes in the presence of DABCO upon ultrasound radiation at room temperature, has been treated with 2,2-dimethoxypropane in the presence of a catalytic amount of cam-phorsulfonic acid to successfully furnish the corresponding oxazolidine 826 in... 

In the synthesis of the B ring of bryostatins. Hale et al. have treated epoxide 33, obtained from the alcohol 32, with a catalytic amount of cam-phorsulfonic acid and THP 34 was produced in 87% yield according to a 6-exo-tet ring closure (Scheme 19) (20000L2189). 

The unusually high conductivity of polyaniline doped with d,l-camphorsulfonic acid has been investigated extensively [38,39]. It has been shown that, d,l-cam-phorsulfonic acid by itself is a poor dopant for polyaniline and that the combination of d,l-camphorsulfonic acid and w-cresol is responsible for high conductivity. The role of w-cresol has led to the concept of secondary... 

Fujise and Sasaki (42) have recorded a peculiar result which appears to fall in this category. Ring closure of IX in the presence of (-f-)-cam-phorsulfonic acid (which presumably acts as an asymmetric catalyst) led to the optically selective formation of X, in which a dissymmetric carbon atom has been generated ... 

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