Mesyloxy group

The syntheses were effected by selective mesylation of one or two hydroxyl groups and displacement of each mesyloxy group by an azido group, which was reduced to amino. Although attempted SN2 displacement of cyclohexane substituents is often unsuccessful, the powerfully nucleophilic azide ion is usually able to displace an alkylsulfonoxy group, and this route has been exploited in several recent cyclitol syntheses. 

Since under these conditions elimination of mesyloxy groups can only occur with participation of the vicinal acetamido group via oxazoline intermediates presupposing iraws-arrangements of the mesyloxy and acetamido moieties, the configuration of (12) and its precursors is unequivocally established. 

Inversion at C-4 The 4 -mesyloxy group in (68) — obtained from (58) in four steps, using standard procedures for acetylation (to (64)), tritylation (65) (66) and mesylation (to (68) — can only be eliminated... 

A. C. Richardson and H. O. L. Fischer, Cyclization of dialdehydes with nitromethane, Part VI. Preparation of 3- amino-1,6-anhydro-3-deoxy-p-D-gulose, -P-D-altrose and -p-D-idose derivatives and their characterization by means of inversion of mesyloxy groups,./. Am. Chem. Soc., 83 (1961) 1132-1139. 

Similarly, various a-D-glucopyranose derivatives having a mesyloxy group at C-4 and an acetoxyl group at C-l are also converted into 1,4-anhydro-/3-D-galactopyranose derivatives on treatment with sodium azide in such aprotic solvents as N,N-dimethylformamide.51 The use of sodium azide in N,N-dimethylformam ide under forcing conditions originated in attempts at nucleophilic displacements to form azido,... 

The iodo derivative is a useful intermediate for the preparation of a wide variety of different types of compounds. Primary mesyl esters also react with sodium iodide in acetone, but the selectivity of this cleavage is less because of the greater reactivity of secondary mesyl esters. oa( ) Methyl 2,3,4-tri-0-acetyl-6-0-mesyl-a-D-glucopyranoside is converted into methyl 2,3,4,6-tetra-O-acetyl-a-D-glucopyranoside with acetic anhydride and potassium acetate. Replacements of a primary mesyloxy group with fluorine by use of potassium fluoride in methanol,106 with chlorine by use of lithium chloride,102 and with pyridine to form a pyri-dinium deoxy derivative,106 have been reported. Primary tosyloxy groups have been replaced by hydrogen,106 by thiocyanate,107 and by... 

An acetal ring reduces the reactivity of the 6-sulfonyloxy group, and two acetal rings may reduce it even more compare, compounds 20 and 21 26 23 and 24 32 and 43. The effect of an acetal ring (on reactivity) is greater with a mesyloxy group than with a tosyloxy group (c/., compounds 20 and 21). 

An alternative synthesis is based on the replacement of the mesyloxy group at C-2 by the hydroxymethyl group with inversion of configuration.400... 

Chiral amino acids.2 The key step in a new synthesis of chiral P-amino acids involves displacement of mesyloxy groups by lithium dialkylcuprates. Thus (S)-... 

Chiral, unsymmetrical divinyl methanols can be prepared by reaction of CH3Cu(CN)Li BF3, prepared from CH3Li, with a monoprotected (E,E)-dienoate such as 1, derived from an L-tartrate. The reaction involves an SN2 reaction with the mesyloxy group. The reaction proceeds readily at —78° with high regio- and (El-stereoselectivity.5... 

Cyclopentadienylmethyl-3-methyl thietane has been obtained by substitution of a mesyloxy group using cyclo-pentadienylmagnesium chloride as nucleophile (Equation 16) <1998JOM433>. 

The introduction of fluorine in the secondary position of carbohydrates, i.e. in the sugar ring skeleton, with potassium fluoride is even more difilcult. However, a 4-mesyloxy group in a gluco configuration, where H5 and H3 are not /ranj-diaxial, can be substituted with potassium fluoride in good yield.Finally, it should be mentioned that F has been introduced in the carbohydrate skeleton by the use of CsHi FJF. ... 

The 12a-mesyloxy-group is eliminated efficiently (80-85%) from the cholic acid derivative (34) to give the A -compound (35), by heating with sodium or potassium acetate in HMPA. ... 

ArOMs — ArH. The reductive removal of mesyloxy groups from an aromatic nucleus with Zn-KI is catalyzed by (Ph Pj NiBr in the presence of dppb. 

Substituent chemical shift values for the acetylation and mesylation of hydroxy-p-benzoquinones and for the introduction of acetyloxy and mesyloxy groups into / -benzoquinones were derived after complete C NMR assign-... 

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