The relationship between methylated chromans and maturity of organic matter in the source rocks from Jianghan hypersaline basin

The distribution,the relative composition,and their variation of methylated chromans(MTTC) with maturation of organic matter in the source rocks from Mingjia 1 well,Jianghan hypersaline basin,have been analyzed and studied. There is a close relationship between the distribution of methylatd chromans and paleosalinity of depositional environment. In the Eq1-Eq3 source rocks deposited under hypersaline environment with lower Pr/Ph ratio,higher gammacerane index and abundant organic sulfur-containing compounds,methyl MTTC and dimethyl MTTC are main components,but in the Eq4 source rocks deposited non-hypersaline environment with relatively higher Pr/Ph ratio,lower gammacerane index and organic sulfur-containing compounds,trimethyl MTTC is a major compound in methylate chromans. Obviously,the distributions and the compositions of methylated chromans in the source rocks are in harmony with biomarker indicators indicating the paleaosalinity and redox of depositional environment. The relationship between the ratio of 5,8-dimethyl MTTC to 7,8-dimethyl MTTC(dimethyl MTTC ratio) and the maturity of organic matter in the source rocks from Mingjia 1 well has been discussed. The results show that dimethyl MTTC ratio increased with the burial depth and the maturation of organic matter in the source rocks,especially in immature level. It is noteworthy that this ratio is very susceptible to small variation in the maturity of organic matter in the source rocks when vitrinite reflectance Ro is less than 0.65%. It may imply that this ratio is a good and susceptible aromatic maturity indicator for the relative maturity of organic matter in immature source rocks.

HFIP-catalyzed highly diastereoselective formal[4+2]cyclization to synthesize difluorinated multisubstituted chromans using difluoroenoxysilanes as C2 synthons

A hexafluoroisopropanol(HFIP)-catalyzed highly diastereoselective formal[4+2]cyclization between ortho-hydroxyphenyl para-quinone methides and difluoroenoxysilanes is developed.This tandem protocol provides a simple and straightforward approach to assemble diverse multiply functionalized difluorinated chromans with high to excellent diastereoselectivity by employing difluoroenoxysilane as a new C2 synthon.

Stable Carbon Isotopic Compositions of Methylated-MTTC in Crude Oils from Saline Lacustrine Depositional Environment:Source Implications

Significantly high abundant methyl-Methyl Trimethyl Tridecyl Chromans （MTTCs） have been detected in aromatic hydrocarbon fractions in crude oils from the Jizhong Depression and Jianghan Basin. The distribution of these compounds is dominated by methyl-MTTC and dimethyl- MTTC series, which indicate diagenetic products of a hypersaline depositional environment in the early stage and show a low degree of methylation. The occurrence of significantly high abundant methyl-MTTC depends mainly on good preservation conditions with a strongly reductive, hypersaline and water-columned depositional environment and subsequent non-intensive diagenetic transformations. The stable carbon isotopic compositions of the methyl-MTTCs and dimethyl-MTTCs in two samples are far different from the stable carbon isotopic composition of C30 hopane of apparent bacteria biogenesis （up to 4.11‰ and 5.75‰, respectively）. This obviously demonstrates that the methyl-MTTC and dimethyl-MTTCs cannot be of bacteria origin, which is different from the previous point of view about non-photosynthetic bacteria products or possible bacteria-reworked products. On the contrary, the stable carbon isotopic compositions of methyl-MTTC and dimethyl-MTTCs in the two samples were similar to that of the same carbon-numbered n-alkanes （nC27-nC28-nC29）, which indicates that they share the same source origin. Especially in the crude oil from the Zhao61 well, stable carbon isotopic compositions are also similar to that of the same carbon-numbered steranes with ααα- 20R isomer （mostly less than 0.4‰）. In consideration of the results of previous studies on saline lake ecological sedimentation, the authors hold that the methyl-MTTC and dimethyl-MTTCs in the saline lake sediments should be of algal biogenesis origin.

Enantioselective Construction of Polycyclic Chromanes through Organocatalytic Sequential Quintuple Reaction via One-Pot Step-Wise Procedure

An efficient and highly stereoselective synthetic method to access polycyclic chromanes has been achieved through organocatalyzed one-pot step-wise reactions involving 2-hydroxycinnamaldehydes,2-aminochalcones,and malononitrile as substrates.The reactions underwent a quintuple process by aza-Michael/Michael/Knoevenagel/oxa-Michael/aldol-type reaction in sequence to give products bearing 3 new generated rings and 5 chiral centers in moderate to quantitative yields with excellent stereoselectivities.

Vasorelaxant effect of 7-[2-(4-morpholinyl)ethoxy]chroman hydrochloride(HEF-04) and possible mechanisms

This study aimed to investigate the relaxant effect of chroman compound HEF-04 on isolated vascular smooth muscle （VSM） and the possible underlying mechanisms involved. Isolated rabbit thoracic aorta was used as the in vitro model and the relaxant effects of HEF-04 on endothelium-intact （＋EC） and endothelium-denuded （EC） thoracic aortic rings were compared. Potassium channel blockers, guanylate cyclase inhibitors, and COX-inhibitors were used to explore associations between the relaxant effects of HEF-04 with potassium channels, NO, and prostaglandin-like substances and endothelial hyperpolafizing factor （EDHF）, respectively. The results indicated that HEF-04 （1 × 10^-5 mol/L to 3× 10^-3 mol/L） had no significant impact on basal vascular tension, but could relax the contraction of vascular smooth muscle caused by high-K＋ solution in a dose-dependent manner. Indomethacin （5.6× 10^-6 mol/L） had no effect on vasorelaxation effect of HEF-04. In contrast, the vasorelaxant effect of HEF-04 was enhanced by methylene blue, which was significantly inhibited by calcium-dependent potassium channel blocker TEA. The vasorelaxant effect of HEF-04 on ＋EC thoracic aortic rings was significantly stronger than that on -EC thoracic aortic rings. The endothelium dependent relaxant effect of HEF-04 on VSM might be attributed to the interaction of HEF-04 with vascular relaxing factors or the increased release of EDHF.

Facile access to chiral 4-substituted chromanes through Rh-catalyzed asymmetric hydrogenation

Rh/ZhaoPhos-catalyzed asymmetric hydroge nation of a series of(E)-2-(chro man-4-ylidene)acetates was successfully developed to prepare various chiral 4-substituted chromanes with high yields and excellent enantioselectivities(up to 99%yield,98%ee).Moreover,the gram-scale hydrogenation could be performed well in the presence of 0.02 mol%catalyst loading(TON=5000),the hydrogenation product was easily converted to access other important compounds,which demonstrated the synthetic utility of this asymmetric catalytic methodology.