Group dithiane protecting

Danishefsky s total synthesis of 317 and its chlorine free precursor monocillin I 316 features an RCM reaction with a substrate 310 that in addition to a dithiane protective group contains a vinyl epoxide and a diene moiety at... 

Thermolysis of 3-(ort o-anisoyl)-l-(l-piperidinyl)-3-cyclobutenes 807 in the presence of mesitylene affords angular-fused xanthones 809 via formation and ring closure of the intermediate 808 (Scheme 226) <1997TL3663>. Linear-fused xanthones 810 are prepared by nucleophilic addition of aryl and heteroaryl lithiates to dithiane protected benzopyrone-fused cyclobutenediones 811 followed by hydroysis of the dithiane protecting group (Scheme 227) <1996JA12473>. 

Reaction of lithiodithianes with acyl chlorides, esters or nitriles leads to the fOTination 1,2-dicarbonyl compounds in which one of the carbonyl groups is protected as the thioacetal. d76043j44 Optically active amino ketones of type (69) are inepared via acylation of dithiane with an oxazoline-protected (5)-serine methyl ester (Scheme 41). Optically active (5)-2-alkoxy-l-(l,3-dithian-2-yl)-l-propanones were prepaid by the reaction of the corresponding methyl (5)-lactate with 2-lithio-l,3-enantioselective synthesis of (-)-trachelanthic acid. Enantioselective synthesis of L-glyceraldehyde involves the acylation of a dithiane glycolic acid derivative followed by bikers yeast mediated reduction. ... 

Platem M, Steckhan E (1980) Indirect electrochemical processes 10. An effective and mildelectrocatalytic procedure for the removal of 1,3-dithiane protecting groups. Tetrahedron Lett 21 511—514... 

A Pummerer-type reaction was carried out on a dithiane protecting group to liberate the corresponding ketone (eq 30). These were the only reaction conditions which provided any of the desired ketone. 

Further study has been made of the use of the methylthiomethyl group for protection of alcohols in synthesis. Primary and secondary alcohols and tertiary alcohols are converted into methylthiomethyl ethers using dimethyl sulphoxide and AcgO, and de-protection is brought about under neutral conditions with a mercury(n) salt. Under these conditions, a 1,3-dithian moiety or a silyl ether grouping in the same molecule are unaffected. Protection of alcohols as 2-phenylselenoethyl ethers and their de-protection by oxidation has been proposed. ... 

The syntheses of radicicol (3) are based on RCM of a diene-ene system, which avoids the problem of regioselectivity, compatibility with labile groups such as a vinyl epoxide, the dithiane protecting group, and the /Z selectivity [14]. In these... 

A carbonyl group can be protected as a sulfur derivative—for example, a dithio acetal or ketal, 1,3-dithiane, or 1,3-dithiolane—by reaction of the carbonyl compound in the presence of an acid catalyst with a thiol or dithiol. The derivatives are in general cleaved by reaction with Hg(II) salts or oxidation acidic hydrolysis is unsatisfactory. The acyclic derivatives are formed and hydrolyzed much more readily than their cyclic counterparts. Representative examples of formation and cleavage are shown below. 

M (marginal) indicates that the stability of the protected functionality is marginal, and depends on the exact parameters of the reaction. The protective group may be stable, may be cleaved slowly, or may be unstable to the conditions. Relative rates are always important, as illustrated in the following example (in which a monothioacetal is cleaved in the presence of a dithiane), and may have to be determined experimentally. 

Intermediate 10 must now be molded into a form suitable for coupling with the anion derived from dithiane 9. To this end, a che-moselective reduction of the benzyl ester grouping in 10 with excess sodium borohydride in methanol takes place smoothly and provides primary alcohol 14. Treatment of 14 with methanesulfonyl chloride and triethylamine affords a primary mesylate which is subsequently converted into iodide 15 with sodium iodide in acetone. Exposure of 15 to tert-butyldimethylsilyl chloride and triethylamine accomplishes protection of the /Mactam nitrogen and leads to the formation of 8. Starting from L-aspartic acid (12), the overall yield of 8 is approximately 50%, and it is noteworthy that this reaction sequence can be performed on a molar scale. 

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