Efficient and Highly Stereoselective Syntheses of (+)-proto-Quercitol and (-)-gala-Quercitol Starting from the Naturally Abundant (-)-Shikimic Acid.

Efficient and highly stereoselective syntheses of (+)-proto-quercitol and (-)-gala-quercitol starting from the naturally abundant (-)-shikimic acid were described in this article. (-)-Shikimic acid was first converted to the key intermediate by eight steps in 53% yield. It was then converted to (+)-proto-quercitol by three steps in 78% yield and was also converted to (-)-gala-quercitol by five steps in 63% yield. In summary, (+)-proto-quercitol and (-)-gala-quercitol were synthesized from (-)-shikimic acid by 11 and 13 steps in 41 and 33% overall yields, respectively.

Novel stereoselective syntheses of N-octyl-ß-valienamine (NOV) and N-octyl-4-epi-ß-valienamine (NOEV) from (-)-shikimic acid.

N-Octyl-ß-valienamine (NOV) 1 and N-octyl-4-epi-ß-valienamine (NOEV) 2 are potent chemical chaperone drug candidates for the therapy of lysosomal storage disorders. Novel stereoselective syntheses of NOV 1 and NOEV 2 starting from naturally abundant (-)-shikimic acid are described in this article. The common key intermediate compound 5 was first synthesized from readily available (-)-shikimic acid via 9 steps in 50% yield. Compound 5 was then converted to NOV 1via 5 steps in 61% yield, and it was also converted to NOEV 2via 8 steps in 38% yield. In summary, NOV 1 was synthesized via 14 steps in 31% overall yield; and NOEV 2 was synthesized via 17 steps in 19% overall yield.

Effect of Modified Polyvinyl Alcohol Fibers on the Mechanical Behavior of Engineered Cementitious Composites.

：Polyvinyl alcohol (PVA) fiber was proposed to enhance the mechanical performance of engineered cementitious composite in this research. A mixture of engineered cementitious composite with better expected performance was made by adding 2% PVA fiber. Mechanics tests, including pressure resistance, fracture resistance, and ultimate tensile strength, were conducted. They reveal that the engineered cementitious composites not only exhibit good pressure resistance, but they also exhibit excellent fracture resistance and strain capability against tensile stress through mechanics tests, including pressure resistance, fracture resistance, and ultimate tensile resistance. To further improve the engineered composites' ductility, attempts to modify the performance of the PVA fiber surface have been made by using a vinyl acetate (VAE) emulsion, a butadiene⁻styrene emulsion, and boric anhydride. Results indicated that the VAE emulsion achieved the best performance improvement. Its use in fiber pre-processing enables the formation of a layer of film with weak acidity, which restrains the hydration of adjacent gel materials, and reduces the strength of transitional areas of the fiber/composite interface, which restricts fiber slippage and pulls out as a result of its growth in age, and reduces hydration levels. Research illustrates that the performance-improvement processing that is studied not only improves the strain of the engineered cementitious composites, but can also reduce the attenuation of the strain against tensile stress.

[Contrast sensitivity function in myopic LASIK].

OBJECTIVE: To evaluate near contrast sensitivity function before and after myopic laser in situ keratomileusis (LASIK). METHODS: With FACT 101 test chart, static near contrast sensitivity was measured in randomly selected 47 subjects (93 eyes) before, 1 month and 6 months after LASIK. The contrast sensitivity was measured at 1.5, 3.0, 6.0, 12.0 and 18.0 cycles per degree (c/d) spatial frequency respectively and made comparison in them. RESULTS: The patients achieved the mean uncorrected visual acuity (UCVA) of 1.07 +/- 0.18 and 1.12 +/- 0.20 at postoperative 1-month and 6-months respectively. There was a general reduction in near contrast sensitivity in all spatial frequencies at postoperative 1-month when they were compared with the preoperative contrast sensitivity. The difference at 12 and 18 c/d spatial frequency was statistically significant (t test, P < 0.01). By the 6-month visit, all eyes showed a recovery of static contrast sensitivity function. The group of high myopia (preoperative > or = -6.00 D) and group with complaining of glare and halos after the surgery had a higher decrease rate of contrast sensitivity compared with that of the group preoperative < - 6.00 D and the group of patients without such complaints respectively. The differences at 6.0, 12.0 and 18.0 c/d spatial frequency at 1-month visit was statistically significant (t test, P < 0.05). CONCLUSIONS: The contrast sensitivity function test offers a more sensitive and comprehensive measure of functional vision than does standard Snellen acuity. The near contrast sensitivity in post-LASIK patients at early stage is reduced despite normal visual acuity and this can affect the quality of vision.

[High throughput screening method of nitric oxide synthase inhibitors and enhancers].

AIM: In order to discover new inhibitors and enhancers of nitric oxide synthase (NOS), an in vitro assay to determine NOS activity was established for high throughput screening. METHODS: The activity of NOS was detected based on the change of nicotinamide-adenine dinucleotide phosphate (NADPH) concentration in the reaction system by the fluorescence density. The enzyme was prepared from bovine brain by gradient centrifugation. The reaction performed in black 96 well micro-plate with a final volume of 90 microL. Every factor which would affect the results such as the concentration of NADPH, L-arginine (L-Arg, used as substrate) and enzyme protein was optimized in different conditions. At last, 5,600 samples (compounds and extracts) were screened by the method. RESULTS: The test signal (fluorescence density) in the reaction system was influenced by many different factors such as temperature and concentration of substrates. The ideal system contains protein 1.50 mg.mL-1, L-Arg 1 mmol.L-1, NADPH 0.1 mmol.L-1 at 37 degrees C. In this method, there were about 2% samples which emit fluorescence, and about 0.5% samples which quench the fluorescence. So these samples were deleted from the sample library. The effects of these samples on activity of NOS were distributed in a normal manner. About 2% samples had potential effects on the NOS activity (including inhibitors and enhancers). CONCLUSION: The method can be performed by high throughput screening and gives the stable data, not only for inhibitors, but also for enhancers of NOS activity.