Thiohydroxamic acids synthesis

The following discussion of hydroxamic acids includes saturated systems, e.g., 2, compounds such as 3, derived from aromatic systems, 7V-hydroxyimides such as 7V-hydroxyglutarimide (78), and certain of their derivatives including thiohydroxamic acids. Naturally occurring cyclic hydroxamic acids are discussed to show the range of structural types that has been found, hut macrocyclic polyhydroxamic acids are mentioned very briefly, because several comprehensive reviews of these compounds are already available. The main purpose of this review is to summarize the methods available for the synthesis of cyclic hydroxamic acids, to outline their characteristic reactions, and to present some useful physical data. Their synthesis and some biological properties have previously been reviewed by Coutts. ... 

The high electrophilicity of dithioesters towards amines was applied to the synthesis of phosphonothioamides [35, 36] and thiohydroxamic acids [37]. Dithioacid salts may also be used as starting materials for this thio-acylation with catalysis by boron trichloride [38]... 

The reactions based on A-hydroxy-2-thiopyridone derivatives are clearly radical chain reactions. In a recent paper,91 we have reported quantum yield measurements for a number of reactions based on iV-hydroxy-2-thiopyridone. Most of the reactions had quantum yields of 10-30. Synthesis of the N-hydroxyquinazolin-4-thione 139 (Ar = Ph, An, 1-Naph) by an improved route gave thiohydroxamic acids which were more sensitive to light than iV-hydroxy-2-thiopyridone. The quantum yield for bromination was in the range 30-60. More important, while the JV-hydroxy-2-thiopyridone system at — 30 °C, makes21 radicals only in a non-chain fashion, the derivatives of 139 continue radical chain reactions even at — 60 °C. 

Gandhi, N.N. Sawant, S.B. Joshi, J.B. Studies on the lipozyme catalysed synthesis of butyl laurate. Biotechnol. Bioeng. 46,1-12 (1995). Al-Mulla E.AL Yunus W.M.Z. Ibrahim N.A. Abdul Rahman M.Z. Enzymatic Synthesis of Palm Olein-based Fatty Thiohydroxamic Acids. 7. Oieo sci., 59, 569-573 (2010). 

Togo and Yokoyama developed a general and efficient method for the synthesis of C-nucleosides employing radical coupling pathways.53 -b Several of these C-nucleosides have been synthesized by ionic pathways but they require many steps and suffer a lack of generality. The thiohydroxamates derived from pentose or 2-tetrahydrofuryl carboxylic acid, Scheme 31, gave the corresponding C-nucleoside derivatives 77 in the presence of an appropriate heteroaromatic compound.53b... 

Hexenyl radicals cyclize to cyclopentylmethyl radicals (see Volume 4, Chapter 4.2). Thus radical decarboxylation of 6-heptenoic acids, by whatever means, usually results in die formation of five-mem-v beied rings. Although this fact had been appreciated previously it is only recendy, widi the advent of the 0-acyl thiohydroxamates, that it has been exploited from a syndietic point of view. An example is provided by the synthesis of bicyclo[4.3.0]proline derivatives from aspartic acid carried out by the Barton group (equation 51). It will be noted that activation of die C—C double bond acting as a radical trap is not necessary in these intramolecular reactions. 

The last and the seventh synthesis of chaetomellic acid A was reported in 1997 by the Samadi group from CNRS, France [81]. This one step synthesis involves a Barton radical decarboxylation and gave 77% overall yield (Scheme 8). The method requires preparation of a thiohydroxamic ester of the corresponding alkyl acid followed by in-situ irradiation in the presence of citraconic anhydride and silica gel chromatography. The last intermediate in this synthesis is similar to the synthesis reported by Branchaud and Slate [75,76]. 

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