The synthesis of chlorodeoxyhexofuranoid derivatives

Regio- and Diastereoselective Allenylation of Aldehydes in Aqueous Media: Total Synthesis of (+)-Goniofufurone(1)

The regio- and diastereoselectivities of metal-mediated allenylation of carbonyl compounds were investigated in aqueous media. Different metal mediators showed varied regioselectivities on product formation during propargylation-allenylation reactions of carbonyl compounds with simple propargyl bromide. Under the standard reaction conditions, the use of indium provided the highest regioselectivity, with a preference of formation of the homopropargyl alcohol. The use of tin and bismuth as the metal mediator provided slightly lower selectivities with the same preference. The use of zinc and cadmium as the mediators further lowered the product selectivity. The reactions of an aliphatic aldehyde with simple propargyl bromide showed a lower selectivity than the reaction of an aromatic aldehyde in most cases, except for the use of tin or zinc (where comparable selectivities were observed). On the other hand, the reaction of terminal-substituted propargyl bromides with aldehydes mediated by indium showed a high regioselectivity in forming allenylation products. The indium-mediated allenylation of carbonyl compounds bearing an alpha-hydroxyl group also proceeded with a high diastereoselectivity, forming syn-diols predominantly in aqueous ethanol. The high diastereoselectivity in allenylation of alpha-hydroxyl-substituted aldehydes was attributed to the chelation effect exhibited by the alpha-hydroxyl substitutent. Through the use of this highly diastereoselective allenylation, (+)-goniofufurone was synthesized from D-glucurono-6,3-lactone.

Influence of monosaccharide derivatives on liver cell glycosaminoglycan synthesis: 3-deoxy-D-xylo-hexose (3-deoxy-D-galactose) and methyl (methyl 4-chloro-4-deoxy-beta-D-galactopyranosid) uronate

An improved, convenient synthesis of 3-deoxy-D-xylo-hexose (3-deoxy-D-galactose) has been developed, and the chemical synthesis of a novel monosaccharide derivative, methyl (methyl 4-chloro-4-deoxy-beta-D-galactopyranosid)uronate (compound 10), is described. Using primary hepatocytes in culture, each was used to explore its effect on glycosaminoglycan (GAG) synthesis. In the absence of analogues hepatocytes synthesize primarily (92-95%) heparan sulphate. At 1 mM, 3-deoxy-D-galactose had little observable effect on either liver cell GAG or protein synthesis. At 10 mM and 20 mM, 3-deoxy-D-galactose reduced [3H]glucosamine and 35SO4 incorporation into hepatocyte cellular GAGs to, respectively, 75% and 60% of the control cells. This inhibition of GAG synthesis occurred without any effect on hepatocyte protein synthesis, indicating that 3-deoxy-D-galactose's effect on GAG synthesis is not mediated through an inhibition of proteoglycan core protein synthesis. Furthermore, GAGs in the presence of 20 mM of the analogue were significantly reduced in size, 17 kDa vs. 66 kDa in untreated cells. These results reflect either impaired cellular GAG chain elongation, and/or altered GAG chain degradation. Compound 10 exhibited a concentration-dependent inhibition of both hepatocyte cellular GAG and protein synthesis. At concentrations of 5, 10 and 20 mM, compound 10 inhibited GAG and protein synthesis by 20, 65 and 90%, respectively. Exogenous uridine was able to restore partially the inhibition of protein synthesis, but was unable to reverse the effect of compound 10 on GAG synthesis. These results show that part of the effect of compound 10 on GAG synthesis is not mediated by an inhibition of proteoglycan core protein synthesis. GAGs in the presence of compound 10 are half as large as those in the absence of this compound (33 and 66 kDa, respectively). These results again may reflect either impaired cellular GAG chain elongation and/or altered GAG chain degradation. Potential metabolic routes for each analogue's effect are presented.