Relevant articles and documents
1,4-DIAMINO-1,4-DIDEOXY-D-GALACTITOL AND 1,5-DIAMINO-1,5-DIDEOXY-L-ALTRITOL
Kuszmann Janos
The mesyloxy group of 1-azido-1-deoxy-4-O-mesyl-D-glucitol could be displaced by azide, in the 2,3:4,5-di-O-isopropylidene derivative 4 or tetraacetate, yielding, after removal of the protecting groups, 1,4-diazido-1,4-dideoxy-D-galactitol (7).The 2,3- (10( and 5,6-O-isopropylidene derivative (13) of 7 gave, on mesylation, the corresponding 5,6- (11) and 2,3-dimesylate (15), respectively.Treatment of 11 with hydrochloric acid yielded 3,6-anhydro-1,4-diazido-1,4-dideoxy-5-O-mesyl-D-galactitol, whereas 15 gave the corresponding 5,6-diol which was converted with base into 2,6-anhydro-1,4-diazido-1,4-dideoxy-3-O-mesyl-D-talitol.Cleavage of the 5,6-O-isopropylidene group of 4 gave 1-azido-1-deoxy-2,3-O-isopropylidene-4-O-mesyl-D-glucitol, which could be converted via the corresponding 4,5-epoxide into 1,5-diazido-1,5-dideoxy-2,3-O-isopropylidene-L-altritol (25).The 6-p-nitrobenzoates of 25 and 13 are derivatives suitable for the synthesis of sorbistin analogues.Reductionof the corresponding deprotected diazides afforded the title compound.
Studies on a dithiane-protected benzoin photolabile safety catch linker for solid-phase synthesis
Hong Boon Lee Balasubramanian
Substituted benzoinyl systems 8a-g, differing either in the substitution pattern, type of resin matrix used, or resin loading capacity, were prepared and the kinetics of their photolytic cleavage of Fmoc-β-alanine examined on resin. The linker systems 6a-g were assembled in near-quantitative yield using Corey-Seebach dithiane addition. The dithiane group that serves as a safety catch against premature photoreaction was removed by either oxidation or alkylation. Analytical methods that include FTIR and 13C gel-phase NMR spectroscopy were used for rapid reaction monitoring and sample characterization on resin. A survey of different substituted systems 8c-f for releasing Fmoc-β-alanine confirmed that the 3-alkoxybenzoin linker photocleaves most rapidly to give the highest yield (τ(1/2) = 6.7 min; 98% yield). Lowering the resin loading from 0.59 mmol/g in 8a to 0.26 mmol/g in 8b improved the cleavage kinetics to τ(1/2) = 2.6 min, 92% yield. Tentagel resin 8g exhibits similar photocleavage kinetics in both organic and aqueous media and when compared to the polystyrene counterpart, 8a. The 3- alkoxybenzoin linker 6a was also loaded with aryl carboxylic acids (12h,i) and hindered Fmoc-protected amino acids (12j-l) with varying degrees of success (57-100%) and dithiane deprotected (70-80%, 13h-1) followed by photocleavage with comparable efficiencies (8993% after 60 min).
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