The truth about false unicorn (Chamaelirium luteum): total synthesis of 23R,24S-chiograsterol B defines the structure and stereochemistry of the major saponins from this medicinal herb

Chamaelirium luteum is used in traditional medicine systems and commercial botanical dietary supplements for the treatment of female reproductive health problems. Despite the wide use of this herb, only very limited phytochemical characterisation is available. Our investigation of C. luteum roots led to the isolation of two new steroidal saponins 1 and 2 that contain an unusual aglycone 3 . The absolute configurations of these molecules were unable to be determined spectroscopically and thus the total synthesis of 3 was undertaken and achieved in 16 steps and 1.6 % overall yield from pregnenolone. The key step in the synthesis was the stereoselective installation of the side chain at C‐17 and C‐20, which employed anion‐accelerated oxy‐Cope methodology. The relative configuration of aglycone 3 was determined by X‐ray crystallography of an advanced synthetic intermediate. The absolute configuration was based upon that of the pregnenolone‐derived steroidal skeleton and determined to be 23R,24S.     

Molecular AND and INHIBIT gates based on control of porphyrin fluorescence by photochromes

A molecular triad consisting of a porphyrin (P) covalently linked to two photochromes-one from the dihydroindolizine family (DHI) and one from the dihydropyrene family (DHP)-has been synthesized and found to act as either a molecular AND logic gate or an INHIBIT gate, depending on the inputs and initial state of the photochromes. The basis of these functions is quenching of porphyrin fluorescence (output of the gates) by the photochromes. The spiro form of DHI does not quench porphyrin fluorescence, whereas its betaine isomer strongly quenches by photoinduced electron transfer. DHP also quenches porphyrin fluorescence, but its cyclophanediene isomer does not. The triad has been designed using suitable energetics and electronic interactions, so that although these quenching phenomena may be observed, independent isomerization of the attached photochromes still occurs. This makes it possible to switch porphyrin fluorescence on or off by isomerization of the photochromes using various combinations of inputs such as UV light, red light, and heat.     

High‐throughput functional marker assay for detection of Xa/xa and fgr genes in rice (Oryza sativa L.)

We apply CE for high‐throughput analysis of functional markers for marker‐assisted selection in rice. The accuracy, throughput and reproducibility of CE analysis for sequence‐tagged site (STS) and simple sequence repeat (SSR) markers for bacterial blight resistance and aroma genes are demonstrated by using a CE system. Multiplex PCR products displayed well‐differentiated allelic variants using different STS and SSR markers for identification of xa13, Xa21 and fgr genes using the CE system compared to 1.2% agarose gel images. Moreover, consumption of PCR product is much less in the CE system compared to traditional agarose gel systems. Sample consumption is less than 0.1 μL per analysis, thereby conserving samples for further downstream analysis. Out of 29 genotypes in BC₁F₃ generation, 16 plants were found homozygous for all the three genes, viz., xa13, Xa21 and fgr. These homozygous lines can be used as potential donors in rice breeding programmes.