Lead tetraacetate oxidation, comparison

The hydrolysis of these model precursors was studied at 37 , with catalysis by hog liver esterase. The major product, isolated in 60-70% yield from the hydrolysis of a-acetoxyNPy, was 2-hyd oxy-tetrahydrofuran. This compound was identified by comparison to a reference sample,prepared by lead tetraacetate oxidation of 1,2,5-pentanetriol (53). Additional evidence was obtained by lithium aluminum hydride reduction of the product to 1,4-butanediol. Minor amounts of butenals were also identified as products of the hydrolysis of a-acetoxy IPy. 

Methoxyvincamine (vincine, XXXV R = OMe), whose ring A methoxyl is so placed because of its UV-spectrum and a color reaction specific for that position, had properties (Chart III) that paralleled those of vincamine (21). This conclusion was reached independently on the basis of mass spectral comparisons (18). The stereochemistry of both alkaloids is regarded as being the same (21). Tetradehydro compounds (XXXVII) were formed by lead tetraacetate oxidation, and XXXVII... 

The practice of using an insoluble polymer to isolate and kinetic-ally stabilize a reactive intermediate has been addressed in several reports, most commonly using DVB cross-linked polystyrene as a support. In these cases, the three dimensional structure of the polymer and rigidity of the polymer backbone diminish intramolecular reactivity between two sites on the same polymer bead. Physical constraints preclude any significant reaction between two different polymer beads. Similar, less dramatic reduced intramolecular reactivity has also been noted for reactive intermediates bound to linear polystyrene. For example, o-benzyne bound to linear polystyrene has been shown by Mazur to have enhanced stability relative to non-polymer-bound -benzyne (35). In this case, o-benzyne was generated by lead tetraacetate oxidation of a 2-aminobenzotriazole precursor, 1. Analysis of the reaction products after cleaving the benzyne derived products from the polymer by hydrolysis showed a 60% yield of aryl acetates was obtained (Equation 11). In contrast, the monomeric aryne forms only coupled products under similar conditions. Further comparisons of the reactivity of -benzyne bound to insoluble 2% or 20%... 

The UV spectrum [2max 256 (sh), 336, 433, and 634 nm] of arcyriaverdin C (355) indicated the presence of a bisindolylmaleimide framework with an extended conjugation (252). The structure of arcyriaverdin C (355) was confirmed by chemical correlation of arcyriaverdin C (355) with arcyriarubin C (351) (see Scheme 2.90) by oxidation of the latter with lead tetraacetate in chloroform. Based on these data, and spectroscopic comparison with the oxidation product of arcyriarubin C (351), the structure 355 was assigned to arcyriaverdin C (252) (Scheme 2.91). 

The inner etherification induced in the sorbitol and D-mannitol structures during polyester formation, made a study of their inner ethers or anhydrides a matter of practical significance. A new monoanhydride of sorbitol was described (21) and designated arlitan (from the initials of the Atlas Research Laboratory). Identification as 1,4-anhydro-D-glucitol was made by comparison of its sirupy tetramethyl ether with that obtained by acid anhydrization of Irvine s 2,3,5,6-tetramethyl-D-glu-citoP by oxidation of the tetramethyl ether to dimethyl-L-threaric acid [0-dimethyl-L-((iea tartaric acid] and identification as the crystalline diamide and by its behavior on oxidation with lead tetraacetate. ... 

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