3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have rec...3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have recently developed a strategy to achieveα-stereocontrolled glycosylation using a C3-p-tolylthio-substituted Kdo phosphite donor.The wide substrate scope and high reactivity of the donors enabled the efficient synthesis of a series of Kdo-containing glycosides with completeα-stereoselectivity and without the formation of 2,3-ene byproducts.In this study,we improved the method by replacing the leaving group diethyl phosphite with fluoride,which enhanced the stability of the donor and led to cleaner reaction.Furthermore,the substrate range was expanded by synthesizing a series of Kdo O/C/S/Nglycosides,which also opened up a new avenue for the synthesis of CMP-Kdo synthase inhibitors.展开更多
应用便携式近红外光谱仪采集320份生鲜猪肉在近红外光谱中波区的光谱信息,采用不同优化方法建立猪肉胆固醇预测模型,并对异常样品的剔除及组合预处理方法对模型性能的改善进行了分析。研究表明:通过对异常值的二次剔除,并使用SG一阶导数...应用便携式近红外光谱仪采集320份生鲜猪肉在近红外光谱中波区的光谱信息,采用不同优化方法建立猪肉胆固醇预测模型,并对异常样品的剔除及组合预处理方法对模型性能的改善进行了分析。研究表明:通过对异常值的二次剔除,并使用SG一阶导数(savitzky-golay first derivative,SG 1st D)、SG平滑(savitzky-golay smoothing,SGS)和正交信号校正(OSC)的组合预处理方法,可获得最佳生鲜猪肉胆固醇预测模型,其参数如下:校正集相关系数(Rc)=0.9137,校正标准差(standard error of calibration,SEC)=2.5607,验证集相关系数(Rp)=0.656 7,预测标准差(standard error of prediction,SEP)=4.985 5,主因子数(principal factor,PF)=4,范围误差比(ratio of performance to standard deviation,RPD)=2.5032,相对预测标准差(relative standard error of prediction,RSEP)=8.625 4%,SEP/SEC=1.946 8,说明模型在近红外光谱中波区对猪肉胆固醇的分辨能力和预测准确度较好,通过向校正集中补充代表性样品可使模型稳健性进一步改善。对检验集样品预测值(prediction value,PV)与参比值(reference value,RV)的t检验显示二者之间无显著性差异(p>0.05),检验集样品总体预测准确率为62.5%,其中50~70mg·(100g)-1区段的局部预测准确率达到91.7%,可以用于生鲜猪肉胆固醇浓度的在线快速初步定量分析。该研究将便携式近红外光谱用于在近红外中波区对生鲜猪肉及肉制品中胆固醇浓度的分析和检测,通过进一步的研究和改进,可将其应用于产品的原料分级、品质和过程控制及市售产品的抽检等。展开更多
从云南美登木内生真菌Phomopsis species Lz42的琼脂平板发酵物中分离得到2个倍半萜和5个麦角甾醇类化合物(1～7),其中化合物1和2为新化合物.应用波谱技术确定其结构为4-Deacetyl-10-oxo-di-hydrobotrydial(1)和麦角甾-6,22-二烯-5α,8...从云南美登木内生真菌Phomopsis species Lz42的琼脂平板发酵物中分离得到2个倍半萜和5个麦角甾醇类化合物(1～7),其中化合物1和2为新化合物.应用波谱技术确定其结构为4-Deacetyl-10-oxo-di-hydrobotrydial(1)和麦角甾-6,22-二烯-5α,8α-环二氧-3-甲酸酯(2).展开更多
基金supported by the National Key R&D Program of China(Nos.2022YFF1203005,2022YFC2303700)supported by the National Natural Science Foundation of China(Nos.81930097,82151223).
文摘3-Deoxy-D-manno–oct-2-ulosonic acid(Kdo)is widely distributed in bacteria,and the synthesis of Kdocontaining oligosaccharides is important for the development of novel antibiotics and immunological agents.We have recently developed a strategy to achieveα-stereocontrolled glycosylation using a C3-p-tolylthio-substituted Kdo phosphite donor.The wide substrate scope and high reactivity of the donors enabled the efficient synthesis of a series of Kdo-containing glycosides with completeα-stereoselectivity and without the formation of 2,3-ene byproducts.In this study,we improved the method by replacing the leaving group diethyl phosphite with fluoride,which enhanced the stability of the donor and led to cleaner reaction.Furthermore,the substrate range was expanded by synthesizing a series of Kdo O/C/S/Nglycosides,which also opened up a new avenue for the synthesis of CMP-Kdo synthase inhibitors.
文摘应用便携式近红外光谱仪采集320份生鲜猪肉在近红外光谱中波区的光谱信息,采用不同优化方法建立猪肉胆固醇预测模型,并对异常样品的剔除及组合预处理方法对模型性能的改善进行了分析。研究表明:通过对异常值的二次剔除,并使用SG一阶导数(savitzky-golay first derivative,SG 1st D)、SG平滑(savitzky-golay smoothing,SGS)和正交信号校正(OSC)的组合预处理方法,可获得最佳生鲜猪肉胆固醇预测模型,其参数如下:校正集相关系数(Rc)=0.9137,校正标准差(standard error of calibration,SEC)=2.5607,验证集相关系数(Rp)=0.656 7,预测标准差(standard error of prediction,SEP)=4.985 5,主因子数(principal factor,PF)=4,范围误差比(ratio of performance to standard deviation,RPD)=2.5032,相对预测标准差(relative standard error of prediction,RSEP)=8.625 4%,SEP/SEC=1.946 8,说明模型在近红外光谱中波区对猪肉胆固醇的分辨能力和预测准确度较好,通过向校正集中补充代表性样品可使模型稳健性进一步改善。对检验集样品预测值(prediction value,PV)与参比值(reference value,RV)的t检验显示二者之间无显著性差异(p>0.05),检验集样品总体预测准确率为62.5%,其中50~70mg·(100g)-1区段的局部预测准确率达到91.7%,可以用于生鲜猪肉胆固醇浓度的在线快速初步定量分析。该研究将便携式近红外光谱用于在近红外中波区对生鲜猪肉及肉制品中胆固醇浓度的分析和检测,通过进一步的研究和改进,可将其应用于产品的原料分级、品质和过程控制及市售产品的抽检等。
文摘从云南美登木内生真菌Phomopsis species Lz42的琼脂平板发酵物中分离得到2个倍半萜和5个麦角甾醇类化合物(1～7),其中化合物1和2为新化合物.应用波谱技术确定其结构为4-Deacetyl-10-oxo-di-hydrobotrydial(1)和麦角甾-6,22-二烯-5α,8α-环二氧-3-甲酸酯(2).
