Oxidations with Lead Tetraacetate

Total Synthesis of (−)-Spirotryprostatin B: Synthesis and Related Studies

“…When 46 was submitted to standard dihydroxylation conditions (OsO 4 (4 mol%), NMO·H 2 O), diol 48 was obtained . Cleavage of diol 48 by treatment with Pb(OAc) 4 was carried out without its prior purification and cleanly afforded aldehyde 49 in 97% yield over two steps . Subsequent oxidation of aldehyde 49 to the corresponding acid 50 following Lindgren's procedure , and conversion to the methyl ester with diazomethane afforded 51 …”

“…Interestingly, although the 1 H NMR spectra of all earlier intermediates were complicated by the presence of multiple rotamers due to restricted amide rotation for the Boc group, analysis of the spectra for 54 was simplified, as sharp resonances were uniformly observed (Scheme ). From 54 , aldehyde 55 was obtained following glycol cleavage with Pb(OAc) 4 . Aldehyde 55 proved remarkably stable, no doubt likely as a result of the sterically hindered environment where it resides, allowing us focus on the critical olefination step.…”

Determination of the composition of organic layers chemically bonded on silicon dioxide

“…This conclusion is consistent with experimental fact. In (5) 3.5% 0.003 ± 0.033 (3) 2.6% 0.009 ± 0.023 (7) methods ± 95 ( ) 0 The symbols Bu and F mean that butyl or fluoro derivatives were chromatographed. The analyzed samples correspond to about 20 m2: 100-150 mg treated Cabosil with a specific area of 170 m2 g"1 Average of two determinations, single determinations are indicated in parentheses for the HF method.…”

“…Division by the total surface concentration gives, after simplification, the relative excess of A: Studies on the dynamic response of ion-selective electrodes are important from both practical and theoretical aspects. However, if kinetic information is intended to be drawn from transient signals (1)(2)(3)(4)(5)(6)(7)(8)(9)(10) caused by an activity step, then one must face a number of difficulties (11)(12)(13)(14), e.g., the disturbing effect of streaming and diffusion potential changes as well as the drift of emf values.…”

Sodium Hypochlorite Pentahydrate as a Reagent for the Cleavage of trans-Cyclic Glycols

“…In general, the cleavage of sterically hindered cyclic glycols, especially trans -glycols, is not easy using reagents other than Pb­(OAc) 4 . However, there are serious drawbacks when using Pb­(OAc) 4 .…”