With Swem oxidant

The widely used Moifatt-Pfltzner oxidation works with in situ formed adducts of dimethyl sulfoxide with dehydrating agents, e.g. DCC, AcjO, SO], P4O10, CCXTl] (K.E, Pfitzner, 1965 A.H. Fenselau, 1966 K.T. Joseph, 1967 J.G. Moffatt, 1971 D. Martin, 1971) or oxalyl dichloride (Swem oxidation M. Nakatsuka, 1990). A classical procedure is the Oppenauer oxidation with ketones and aluminum alkoxide catalysts (C. Djerassi, 1951 H. Lehmann, 1975). All of these reagents also oxidize secondary alcohols to ketones but do not attack C = C double bonds or activated C —H bonds. 

The aldehyde function at C-85 in 25 is unmasked by oxidative hydrolysis of the thioacetal group (I2, NaHCOs) (98 % yield), and the resulting aldehyde 26 is coupled to Z-iodoolefin 10 by a NiCh/CrCH-mediated process to afford a ca. 3 2 mixture of diaste-reoisomeric allylic alcohols 27, epimeric at C-85 (90 % yield). The low stereoselectivity of this coupling reaction is, of course, inconsequential, since the next operation involves oxidation [pyridinium dichromate (PDC)] to the corresponding enone and. olefination with methylene triphenylphosphorane to furnish the desired diene system (70-75% overall yield from dithioacetal 9). Deprotection of the C-77 primary hydroxyl group by mild acid hydrolysis (PPTS, MeOH-ClHhCh), followed by Swem oxidation, then leads to the C77-C115 aldehyde 28 in excellent overall yield. 

New procedures to the formation of l,4-dioxa-7,l 1-dithiacyclotridecan-9-ol and 1,4,7-trioxa-10,14-dithiacyclohexadecaen-12-ol utilized 2,3-dibromopropanol with either (CH2OCH2CH2SH)2 or 0(CH2CH20CH2CH2SH)2 with Li2C03 in aqueous EtOH the procedure was shown to proceed via an oxirane intermediate <06CHC206>. The convenient oxidation of the above tridecan-9-ol to the l,4-dioxa-7,ll-dithiacyclotridecan-9-one was accomplished by a Swem oxidation at low (-70 °C) temperatures the alkylation and acylation of the ring alcohol moieties were also reported therein. 

Stilbenes, photocyclization of, 30, 1 StiUe reaction, 50, 1 Stobbe condensation, 6, 1 Substitution reactions using organocopper reagents, 22, 2 41, 2 Sugars, synthesis by glycosylation with sulfoxides and sulfinates, 64, 2 Sulfide reduction of nitroarenes, 20, 4 Sulfonation of aromatic hydrocarbons and aryl halides, 3, 4 Swem oxidation, 39, 3 53, 1... 

Tezacitabine is also an inhibitor of RNDR and it is currently undergoing Phase III development for cancer. Its inhibition mechanism is detailed in Chapter 7. Tezacitabine is synthesized from the cytidine protected at 4 -OH, 5 -OH, and 4-NH2. The Swem oxidation provides a ketone that is converted to a gem-fluoro-sulfonyl olefin with the anion of sulfonylfluorophosphonate. Reduction of the sulfonyl group was realized with Bu3SnH (Figure 8.4). ... 

The silyl protecting group is cleaved with TBAF in THE and the resulting free alcohol is then convened into aldehyde 9 by a Swem oxidation. 

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