Summary Photochemical transformations enable exquisite spatiotemporal control over biochemical processes; however, methods for reliable manipulations of biomolecules tagged with biocompatible photo-sensitive reporters are lacking. Here we created a high-affinity binder specific to a photolytically removable caging group. We utilized chemical modification or genetically encoded incorporation of noncanonical amino acids to produce proteins with photocaged cysteine or selenocysteine residues, which were used for raising a high-affinity monoclonal antibody against a small photoremovable tag, 4,5-dimethoxy-2-nitrobenzyl (DMNB) group. Employing the produced photocage-selective binder, we demonstrate selective detection and immunoprecipitation of a variety of DMNB-caged target proteins in complex biological mixtures. This combined orthogonal strategy permits photocage-selective capture and light-controlled traceless release of target proteins for a myriad of applications in nanoscale assays.

An efficient method for the synthesis of 4-amino-5-(arylaminomethyl)-2-(methylthio)furo[2,3-d]pyrimidines via the Mitsunobu reaction of 4-amino-5-(hydroxymethyl)-2-(methylthio)furo[2,3-d]pyrimidine with N-mesyl-and N-nosylarylamines, and subsequent removal of the mesyl and nosyl groups, has been developed. The influence of substituents in the arylamine moiety on the Mitsunobu reaction was investigated. An unexpected nucleophilic substitution of a nitro group in the reaction of N-({4-amino-2-(methylsulfonyl)furo[2,3-d]pyrimidin-5-yl}methyl)-4-nitro-Nphenylbenzenesulfonamide with sodium methoxide was observed.

The formation of three oxidative DNA 5-methylcytosine (5mC) modifications (oxi-mCs)—5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC)—by the TET/JBP family of dioxygenases prompted intensive studies of their functional roles in mammalian cells. However, the functional interplay of these less abundant modified nucleotides in other eukaryotic lineages remains poorly understood. We carried out a systematic study of the content and distribution of oxi-mCs in the DNA and RNA of the basidiomycetes Laccaria bicolor and Coprinopsis cinerea, which are established models to study DNA methylation and developmental and symbiotic processes. Quantitative liquid chromatography–tandem mass spectrometry revealed persistent but uneven occurrences of 5hmC, 5fC and 5caC in the DNA and RNA of the two organisms, which could be upregulated by vitamin C. 5caC in RNA (5carC) was predominantly found in non-ribosomal RNA, which potentially includes non-coding, messenger and small RNA species. Genome-wide mapping of 5hmC and 5fC using the single CG analysis techniques hmTOP-seq and foTOP-seq pointed at involvement of oxi-mCs in the regulation of gene expression and silencing of transposable elements. The implicated diverse roles of 5mC and oxi-mCs in the two fungi highlight the epigenetic importance of the latter modifications, which are often neglected in standard whole-genome bisulfite analyses.

Recently we showed that esters of thieno[2,3-d]pyrimidine-6-carboxylic acids are useful precursors for the synthesis of analogues of folic acid and other 6-(arylamino)methylthieno[2,3-d]pyrimidines -potential inhibitors of dihydrofolate reductase [1,2]. Continuing our work on the synthesis of fused heterocycles with anticipated biological and pharmaceutical activities we present herein some findings on the synthesis of 2-alkylthio-4-aminofuro[2,3-d]pyrimidine-5-carboxylates by the reaction of 2-alkylthio-6-aminopyrimidin-4(3H)-ones (1) with ethyl bromopyruvate. There are only few examples of such an approach to furo-[2,3-d]pyrimidine-5-carboxylates [3,4] in the literature and they show that such a cyclocondensation reaction can be performed under basic conditions. However, attempts to apply the described procedures for the synthesis of 3a,b, using triethylamine or K 2 CO 3 as basic reagents, failed. Nevertheless, it was found that the cyclocondensation reaction of 1a,b with an equivalent amount of ethyl bromopyruvate proceeds under neutral or acidic conditions to give furopyrimidines 2a,b in good yields. Formation of the corresponding pyrrolo-[2,3-d]pyrimidines was not observed. When an excess of ethyl bromopyruvate was used and the reaction was carried out at room temperature together with furopyrimidines 2, formation of furo[3,2-e]imidazo[1,2-c]pyrimidines 3 was also observed. For example, 3b was isolated as a side product (0.4%) from the reaction of 1b with 2 eq. of ethyl bromopyruvate.

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