(1S,2S,6S,9S)-6-Methyl-5-oxobicyclo­[4.4.0]decane-2,9-diyl diacetate

The chiral title compound, C15H22O5, is an inter­mediate in the total synthesis of biologically active 9,11-secosterols. In the crystal, the cyclo­hexane rings are trans-fused and both adopt chair conformations. In the crystal, mol­ecules are loosely held together in a layer parallel to (100) by weak inter­molcular C—H⋯O hydrogen bonds accepted by carbonyl O atoms of the acetyl groups

Pelaksanaan Perlindungan Hukum Bagi Awak Kapal pada PT Pelayaran Nasional Indonesia (Pelni) Semarang

Penelitian dari pelaksanaan perlindungan hukum bagi awak kapal pada PT.Pelayaran Nasional Indonesia (Pelni) Semarang ini bertujuan untuk mengetahui pelaksanaan perlindungan hukum bagi awak kapal serta mengetahui dan menganalisis hambatan-hambatan apa saja yang muncul serta upaya apa yang dilakukan PT Pelayaran Nasional Indonesia (Pelni) Semarang dalam menanggulangi hambatan pelaksanaan perlindungan hukum terhadap pekerja atau anak buah kapal. Hasil penelitian ini adalah jika dilihat dari segi perjanjian kerja laut maka tidak mencerminkan kepastian hukum yang pasti. Segi hak waktu kerja, istirahat, dan cuti, PT.Pelni Semarang telah dapat melaksanakan ketentuan dalam Pasal 79 ayat (2) UU Nomor 13 Tahun 2003 tentang Ketenagakerjaan. Segi kesehatan dan keselamatan kerja, PT.Pelni telah sesuai dengan ketentuan dari UU No.1 Tahun 1970 tentang keselamatan kapal dan telah sesuai dengan ketentuan Peraturan Pelaksanaan tentang Kecelakaan Pelaut. Hambatan dalam pelaksanaan perlindungan hukum ini kurangnya kesadaran hukum para pekerja di kapal atau anak buah kapal (ABK), dan Serikat pekerja (SP) dikuasai oleh Perusahaan dan sikap pemerintah pusat yang pasif dalam merespon permasalahan yang berkaitan dengan transportasi laut. Sehingga kesimpulan penulisan ini yaitu dari segi perjanjian kerja laut tidak mencerminkan kepastian hukum yang pasti, hak waktu kerja, istirahat dan cuti, serta segi kesehatan dan keselamatan kerja sudah sesuai dengan ketentuan pelaksanaan perlindungan hukum

Chiral recognition by supramolecular porphyrin-hemicucurbit[8]uril-functionalized gravimetric sensors

Enantiorecognition of a chiral analyte usually requiresthe abilityto respond with high specificity to one of the two enantiomers ofa chiral compound. However, in most cases, chiral sensors have chemicalsensitivity toward both enantiomers, showing differences only in theintensity of responses. Furthermore, specific chiral receptors areobtained with high synthetic efforts and have limited structural versatility.These facts hinder the implementation of chiral sensors in many potentialapplications. Here, we utilize the presence of both enantiomers ofeach receptor to introduce a novel normalization that allows the enantio-recognitionof compounds even when single sensors are not specific for one enantiomerof a target analyte. For this purpose, a novel protocol that permitsthe fabrication of a large set of enantiomeric receptor pairs withlow synthetic efforts by combining metalloporphyrins with (R,R)- and (S,S)-cyclohexanohemicucurbit[8]uril is developed. The potentialitiesof this approach are investigated by an array of four pairs of enantiomericsensors fabricated using quartz microbalances since gravimetric sensorsare intrinsically non-selective toward the mechanism of interactionof analytes and receptors. Albeit the weak enantioselectivity of singlesensors toward limonene and 1-phenylethylamine, the normalizationallows the correct identification of these enantiomers in the vaporphase indifferent to their concentration. Remarkably, the achiralmetalloporphyrin choice influences the enantioselective properties,opening the way to easily obtain a large library of chiral receptorsthat can be implemented in actual sensor arrays. These enantioselectiveelectronic noses and tongues may have a potential striking impactin many medical, agrochemical, and environmental fields

The Breaking of Symmetry Leads to Chirality in Cucurbituril-Type Hosts

Cucurbituril-type hosts are highly symmetric, but there are means to break their symmetry. This review will present examples from three directions of induction of chirality in or by cucurbituril-type hosts: first, through the incorporation of stereogenic elements into host molecules; second, through complexation with achiral guests, which leads to axial supramolecular chirality and helical structures; third, through the formation of complexes with chiral guests in multi-molecule complexes and induction of supramolecular chirality. In addition, a list of chiral guests used in binding studies with cucurbiturils is collected. We would envision that encouraged by the outlined examples of outstanding applications of chiral cucurbituril-supramolecular systems, the boundaries of chiral applications of cucurbiturils would be widened

The Breaking of Symmetry Leads to Chirality in Cucurbituril-Type Hosts

Cucurbituril-type hosts are highly symmetric, but there are means to break their symmetry. This review will present examples from three directions of induction of chirality in or by cucurbituril-type hosts: first, through the incorporation of stereogenic elements into host molecules; second, through complexation with achiral guests, which leads to axial supramolecular chirality and helical structures; third, through the formation of complexes with chiral guests in multi-molecule complexes and induction of supramolecular chirality. In addition, a list of chiral guests used in binding studies with cucurbiturils is collected. We would envision that encouraged by the outlined examples of outstanding applications of chiral cucurbituril-supramolecular systems, the boundaries of chiral applications of cucurbiturils would be widened

Mechanochemical Nucleophilic Substitution of Alcohols via Isouronium Intermediates

An expansion of the solvent-free synthetic toolbox is essential for advances in the sustainable chemical industry. Mechanochemical reactions offer a superior safety profile and reduced amount of waste compared to conventional solvent-based synthesis. Herein we report a new mechanochemical method for nucleophilic substitution of alcohols using fluoro-N,N,N′,N′-tetramethylformamidinium hexafluorophosphate (TFFH) and K2HPO4 as an alcohol-activating reagent and a base, respectively. Alcohol activation and reaction with a nucleophile were performed in one milling jar via reactive isouronium intermediates. Nucleophilic substitution with amines afforded alkylated amines in 40–91% yields. The complete stereoinversion occurred for the SN2 reaction of (R)- and (S)-ethyl lactates. Substitution with halide anions (F−, Br−, I−) and oxygen-centered (CH3OH, PhO−) nucleophiles was also tested. Application of the method to the synthesis of active pharmaceutical ingredients (APIs) has been demonstrated

Size-Control by Anion Templating in Mechanochemical Synthesis of Hemicucurbiturils in the Solid State

Self-organization is one of the most intriguing phenomena of chemical matter. While the self-assembly of macrocycles and cages in dilute solution has been extensively studied, it remains poorly understood in solvent-free environments. Here, we provide the first example of using anionic templates to achieve selective assembly of differently sized macrocycles in a solvent-free system. Using the acid-catalyzed synthesis of cyclohexanohemicucurbiturils as a model system, we demonstrate size-controlled quantitative synthesis of 6- or 8-membered macrocycles, taking place through spontaneous anion-directed re-organization of mechanochemically-obtained oligomers in the solid state.<br /