Deprotection sodium periodate

Epoxidadon of (Z)-vinyl sulfone, which is available from the Peterson olefination of (S)-O-pentylideneglyceraldehyde and phenyl trimethylsilylmethyl sulfone in three steps (40% overall yield), with f-BuOOH/t-BuOK in THE gives epoxy sulfone (eq 2). Deprotection of the ketal group and recrystallization affords an optically pure epoxy diol, which is then treated with sodium periodate followed by sodium borohydride to give an alcohol. Protection of the resulting alcohol as its silyl ether yields l/ ,25)-l-phenylsulfonyl-2- [ fcrf-butyldiphenyl)silyl]oxymethyl oxirane ). Its enantiomer is available in the same manner starting from / )-isopropylideneglyceraldehyde. ... 

A new method for the synthesis oligonucleotides containing of 5-formyl-2 -deoxyuridine has been described. The protected phosphoramidite of 5-(l,2-dihydroxyethyl)-2 -deoxyuridine (181) was prepared from 5-iodo-2 -deoxyuridine in seven steps. Following deprotection of the oligomer, subsequent oxidation of the diol with sodium periodate yielded the formyl function which could also be reduced with sodium borohydride to yield the 5-hydroxymethyl compound. An... 

Acid hydrolysis of 62 gave 63 and 64. Oxidation of 63 with sodium periodate followed by sodium chlorite furnished 65 in 86% yield, whose deprotection with TFA followed by Tesser s base afforded 3. 

Alternatively, compound 14 was oxidized with sodium periodate, followed by reduction with sodium borohydride in ethanol to afford 18 (Scheme 3). Hydrolysis of the isopropy-lidene group in 18 with 50% aqueous trifluoroacetic acid followed by hydrogenation of the azide group and then intramolecular reductive amination and protection of the imine group afforded 19. Selective mesylation of the primary hydroxyl group in 19 followed by silylation and subsequent removal of the benzyloxycarbonyl group and then cyclization with sodium acetate afforded 20. Deprotection of 20 led to me50-quinuclidine-3,5-diol (3). 

A recent publication gives an improved method by which the diol 4.2.1.1 (as its 2 -triethylsilylether) is oxidized selectively to its 6-oxo derivative, which was then epimerized to the 7/ -hydroxy derivative 4.2.I.9. Reduction of 4.2.1.9 with sodium triacetoxyborohydride gave the 6/3,7/3-diol, and this was converted to the a-nitrate 4.2.1 10 by treatment with thionyl chloride and then sodium periodate to give a cyclic sulfate, followed by tetrabutyl ammonium nitrate. Hydrogenolysis of 4.2.1.10 and deprotection gave the metabolite 4.2.1.8 in 37% overall yield from 4.2.1.1 (178). 

Conversely, exposure to hydrogen fluoride at 0 °C over short periods of time leads to almost quantitative hydrolysis.[37-39] In aprotic organic solvents, decomposition takes place unless the sulfate hemi-ester is neutralized with strong counterions.[37,381 The results of a detailed study are summarized in Figures 1 and 2t4°l which show the effect of various acids used in peptide chemistry in deprotection and in cleavage from the resin as well as the effect of temperature on the hydrolysis of tyrosine 0-sulfate as a sodium salt. 

The deprotection of t-Boc proline ester 2a is representative of the general procedure employed, tert-Butyl carbamate (0.217 g, 1.0 mmol) and aluminium chloride (0.134 g, 1.0 mmol) doped on a neutral alumina (1.0 g) were mixed thoroughly on a vortex mixer. The reaction mixture was placed in an alumina bath inside an unmodified household microwave oven (operating at frequency 2450 MHz) and irradiated for a period of 1 min. After completion of the reaction (monitored by TLC, EtOAc-hexane, 9 1 v/v), it was neutralized with aqueous sodium bicarbonate solution and the product was extracted into ethyl acetate (2x15 mL). The ethyl acetate layer was separated, dried over magnesium sulfate, filtered, and the crude product thus obtained was purified by column chromatography to afford pure methyl ester 2b in 88% yield. 

One gram of TMS-capped silica was treated with 15 mL of 0.25 M TMSI in dry acetonitrile at 70° C for a period of at least 12 h. Temperatures of less than40°C (which were sufficient to deprotect systems based on one benzyl carbamate per imprint molecule) did not show appreciable deprotection of material 1. Given the treatment necessary to achieve carbamate deprotection, it is important to emphasize that the TMSI procedure does not change the connectivity of the silica framework, as ascertained by studies on model crystalline materials such as a high-silica zeolite faujasite [42]. Following TMSI treatment, the silica was filtered and washed with acetonitrile, methanol, saturated aqueous sodium bicarbonate, methanol, and acetonitrile. The purpose of the aqueous treatment was hydrolysis of the silyl carbamate intermediate as shown in Fig. 6b-c. 

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