Protective groups, removal oxidative

These reactions only operate on very sensitive substrates, and protecting groups removable under basic conditions normally resist a Swern oxidation. 

Condensation of the D-galactopyranosyl-derived phosphonium salt 60 and aldehyde 61 provides the unsaturated dimer 62 after desilylation and oxidation. Iteration of the sequence twice with phosphonium salt 60 leads to tetramer 63 with, however, low coupling efficiencies (36% for the trimer and 11% for the tetramer) mostly due to the base-induced a,/3-unsaturation of the aldehydic substrates. Protecting group removal and hydrogenation of the carbon-carbon double bonds furnish tetramer 64, a C-mimetic of the /3-(1 6) tetragalactoside similar to the one shown in O Scheme 3. 

The first synthesis of the hexacyclic himandrine skeleton was achieved by L.N. Mander and co-workers. The last six-membered heterocycle was formed via an intramolecular Wacker-type oxidation in which the terminal alkene side-chain reacted with the secondary amine functionality. The oxidation was conducted in anhydrous acetonitrile to insure that the Pd-alkene complex was substituted exclusively by the internal nucleophile. The resulting six-membered enamine was then hydrogenated and the MOM protecting groups removed to give the desired final product. 

Nakajima, N., Tanaka, T, Hamada, T, Oikawa, Y, and Yonemitsu, O., Highly stereoselective total synthesis of pikronolide, the aglicon of the first macrolide antibiotic pikromycin. Crucial role of benzyl-type protecting groups removable by 2,4-dichloro-5,6-dicyanobenzoquinone oxidation, Chem. Pharm. Bull., 35, 2228, 1987. 

Dithiins and some 3-substituted derivatives are obtained from the 1,4-bis-addition of alkylthiols to substituted 1,3-butadiynes and subsequent removal of the thiol protecting group and oxidation of the resulting dithioenolates with iodine (94SL201). This latter oxidative cyclisation is also employed as the flnal step in the total synthesis of the naturally occurring 8 n-electron antiaromatic... 

Protection of alcohol groups as tiglates Removal of protective groups via oxidative cleavage s. 18, 24 OAc OH... 

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