Tetra-, hexa-, and octasaccharide subunits of the [→4)-β-D-Manp-(1→4)-β-D-Xylp-(1→]n xylomannan motif proposed as the structure of a novel non-protein, thermal hysteresis-producing antifreeze substance from the freeze-tolerant Alaskan beetle Upis ceramboides have been accessed by total chemical synthesis. Comparison of their NMR spectral data with data of the isolate lends strong support to the proposed structure. Synthetic tetrasaccharides representing various linkage isomers considered (α- rather than β-manno, and linkage through mannose O3 rather than O4) show more significant chemical shift differences with the isolate and are therefore excluded from further consideration.

Iodoalkyl tert-butyl carbonates and carbamates undergo clean free radical addition to thiomaleic anhydride to give substituted thiosuccinic anhydrides in high yield on treatment with tris (trimethylsilyl)silane and a radical initiator. After removal of the tert-butyloxycarbonyl group cyclization then affords lactones or lactams substituted in the α-position by a thiocarboxylic acid residue. This group is converted to amides through reaction with electron-deficient sulfonamides, or to aldehydes and/or ketones by the reaction of derived thioesters with either thiophenol, an electrondeficient allyl phenyl sulfide, or phenyl boronic acid.

Reaction of thiomaleic anhydride with triphenylphosphine gives the title compound which undergoes reaction with a variety of aldehydes to give a range of alkylidene thiomaleic anhydrides (substituted monothio itaconic anhydrides). Subsequent treatment with tert-butoxycarbonylaminosubstituted thiols, or under radical conditions with tert-butoxycarbonylamino-substituted alkyl halides results in a series of substituted monothiomaleic anhydrides, that on exposure to trifluoroacetic acid and then base lead to thiocarboxyl substituted 1,4-thiazepin-5-ones and piperidinones, respectively, that are ultimately trapped by reaction with 2,4-dinitrobenzenesulfonamides to give the corresponding amides.

Dihydro-3-(triphenylphosphoranylidene)-2,5-thiophendione: A Convenient Synthon for the Preparation of Substituted 1,4-Thiazepin-5-ones and Piperidinones via the Intermediacy of Thioacids. -The title synthon (III) reacts with a series of aldehydes to give monothioitanoic anhydride derivatives such as (V). Conjugate addition reactions of these intermediates with aminothiols or alkyl radicals lead to a series of heterocycles such as (VIII)/(IX), (XII)/(XIII), or (XVI). -(CRICH*, D.; RAHAMAN, M. Y.; Tetrahedron 66 (2010) 33, 6383-6390, http://dx.

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