Syntheses of 2,5-dimethyl-4-naphth-2′-yldioxolanes and their stereoselective isomerization to naphtho[1,2-c]pyrans, angular analogues of glucoside B, a cleavage product of the aphid insect pigments the protoaphins

Benzynes were generated selectively through loss of ortho-bromotosylate from 1,2-dibromo-3- tosylates. Thus when treated with bu tyl lithium in the presence of furan rel -(2 R ,4 S ,5 R )-4-(2',3'- dibromo-5'-methoxy-4'-toluene- p -sulfonyloxyphenyl)-2,5-d imethyl-1,3-dioxolane 21 was converted in two steps into rel -(2 R ,4 S ,5 R )-4-(1'-bromo-4'-methoxynaphthalen-2'-yl)-2,5- dimethyl-1,3-dioxolane 8 in good yield. Attempted stereoselective isomerization of dioxolane 8 with titanium(IV) chloride at low temperature led to the recovery, almost exclusively, of starting material. The debrominated analogue rel -(2 R ,4 S ,5 R )-4-(1'-methoxynaphthalen-3'-yl)-2,5- dimethyl-1,3-dioxolane 31 , on the other hand, isomerized readily to give rel -(1 R ,3 R ,4 S )- and rel - (1 S ,3 R ,4 S )-3,4-dihydro-4-hydroxy-6-met hoxy-1,3-dimethylnaphtho[1,2- c ]pyrans 32 and 34 in a ratio (~1:3) that did not vary with reaction temperature

Ruthenium-catalyzed azide alkyne cycloaddition reaction: scope, mechanism and applications

The ruthenium-catalyzed azide alkyne cycloaddition (RuAAC) affords 1,5-disubstituted 1,2,3-triazoles in one step and complements the more established copper-catalyzed reaction providing the 1,4-isomer. The RuAAC reaction has quickly found its way into the organic chemistry toolbox and found applications in many different areas, such as medicinal chemistry, polymer synthesis, organocatalysis, supramolecular chemistry, and the construction of electronic devices. This Review discusses the mechanism, scope, and applications of the RuAAC reaction, covering the literature from the last 10 years

An investigation into steric factors in the stereoselective formation of naphthopyrans from 4-naphthyldioxolanes

The titanium tetrachloride-induced isomerisation of rel-(2R,4R,5S )- and re/-(2S,4R,5fl)-2,5-dimethyl-4-{8- bromo-4,5,7-trimethoxy-2-naphthyl) dioxolanes 16, having the C-4 oxygen protected by a methyl instead of the previously employed isopropyl group, afforded the desired linear re/-(1fl, 3fl,4fl)-6-bromo-3,4- dihydro-4-hydroxy-7,9,10-tnmethoxy -1 ,3-dimethyM H-naphtho[2,3-c] pyran 20, identified as its acetate 21, as well as the corresponding angular analogue, re/-( 1 fl,3R,4fl)-3,4-dihydro-4-hydroxy-6,7,9-trimethoxy- 1 ,3-dimethylnaphtho [1 ,2-c] pyran 22 also identified as its acetate 23

Asymmetric syntheses of Isochroman-4,7-diols through intramolecular cyclization of tethered lactaldehydes

Ready cyclization through silica gel chromatography of the asymmetric phenolic lactaldehyde (14) afforded the diastereomeric pair of isochroman-4,7-diols (21) and (23) in good yield, while (17), the benzylic epimer of (14), similarly yielded the isochroman-4,7-diol (25) as a single diastereomer

Interim Report: Understanding wastewater treatment technologies for alternative water use: transformation of inorganic and organic nitrogen WP2: Monitoring and Data Collection Research Report No. CWQRC 2016-006 Curtin Water Quality Research Centre.

In this report, we summarise collected data on the occurrence and removal of several anthropogenic chemicals in Western Australian Waste Water Treatment Plants (WWTPs) that differ in geographical location and design. Treatment efficiency was also characterised by monitoring nutrient concentrations. A wide variety of anthropogenic compounds were detected in the WWTPs. Wastewater treatments reduced the concentrations of some of these chemicals to varying extents, while other chemicals were persistent through treatment. While there was no consistent pattern in chemical removal at different WWTPs, preliminary results indicate that the simple pond systems generally performed less effectively compared to oxidation ditch and combined pond systems. Multivariate analysis of the DNA sequencing results indicated that microbiomes (i.e., the microbial DNA) associated with the treatment plants could be differentiated based on location, treatment stage and treatment technology. For 3 out of the 4 plants (WWTP 1, WWTP 3, WWTP 4), all influents were similar, but microbial communities after treatment varied widely, depending on the location or technology. The microbial community of WWTP 2 influent was different from the other treatment plants and the microbial profile remained similar even after treatment

Regioselectivity in the syntheses of Enantiopure 2-Benzopyrans through Intramolecular cyclization of tethered Lactaldehydes. Conformations of the products

Using titanium tetraisopropoxide, the enantiopure tethered lactaldehyde (α′ S,2S)-2-(3′-hydroxy-α′-methyl-benzyloxy)propanal (6) is cyclized with complete regio- and diastereoselectivity ortho to the phenolic hydroxyl group to give (1S,3S,4R)-3,4-dihydro-1,3-dimethyl-2-benzopyran-4,5-diol (7). Similar cyclization of the epimeric (α′ R,2S)-lactaldehyde (25) yields solely the corresponding (1R,3S,4R)-4,5-diol (34). The 4,5-diacetate (26), but not (35), undergoes conformational inversion of the heterocyclic ring through significant 4,5-peri interactions between the adjacent acetoxy substituents. Spontaneous cyclizations of the corresponding phenoxide ions of the lactalde-hydes (6) and (25), generated by fluoride from their silyl ethers, led to the related 4,7-diols with high regioselectivity through ring-closure para to the aromatic oxygen

The effect of acidity on the production of signal molecules by Medicago roots and their recognition by Sinorhizobium

The Medicago sativa–Sinorhizobium symbiosis is challenged by acidity, resulting in generally poor nodulation and production. Medicago murex, however, can nodulate and grow at low pH. The effect of low pH on signal exchange in the Sinorhizobium–Medicago symbiosis was studied to gain a greater understanding of the basis for poor nodulation of M. sativa compared to M. murex. Root exudates from M. sativa and M. murex grown in buffered nutrient solution at pH 4.5, 5.8 and 7.0, were collected to measure the expression of nodB induction in Sinorhizobium. A nodB–gusA fusion was constructed and inserted into Sinorhizobium medicae strains WSM419 (acid tolerant) and CC169 (acid sensitive). We identified greater induction by root exudates from both Medicago spp. collected at pH 4.5 than at pH 5.8 and 7.0, less induction by M. murex than M. sativa and less induction of WSM419 than CC169. The same major inducing compounds, 4′,7-dihydroxyflavanone (liquiritigenin), 4′,7-dihydroxyflavone, and 2′,4′,4-trihydroxychalcone (isoliquiritigenin), were identified in exudates of M. murex and M. sativa at all pH values, although in increasing amounts at lower pH. Poor nodulation of M. sativa relative to M. murex under acid conditions is not the consequence of decreased induction of Sinorhizobium nodB by chemical inducers present in the root exudates of both species at low pH