Synthesis of Functionalised Cyclohexanes from Carbohydrates

<p>Beta-D-glucopyranose pentaacetate was photobrominated to give the 5-baromide from which 6-deoxy-Beta-D-xylo-hex-5-enopyranose tetraacetate was obtained by reductive elimination. This reaction sequence represents an efficient new route to the 5-ene. A detailed investigation into the photobromination of Beta-D-glucopyranose pentaacetate with bromine and with NBS led to the isolation of several by-products containing bromine substituents at C-1 and/or C-5; their reactions with zinc-acetic acid were studied, and the conformations. in solution of four alkenes derived from the 5-bromo compound were determined. 2,3,4-Triacylated 2,3,4,5-tetrahydroxycyclohexanones were Obtained by mercury (II) catalysed rearrangement of 5-deoxyhex-5-enopyranose esters. The mechanism of this rearrangement, and some enopyranose esters The mechanism of this rearrangement, reactions of the products were examined. The use of these new carbocyclic compounds in the synthesis of branched-chain cyclitol derivatives was explored. By means of diazomethane or, alternatively, hydrogen cyanide, substituted cyclohexanes with one-carbon branches and tertiary hydroxyl groups at the site of chain-branching were preared. Attempts to eliminate water from these tertiary alcohols to give substituted cyclohexene-carbonitriles or -carbaldehydes were unsuccessful.</p>

Synthesis of Functionalised Cyclohexanes from Carbohydrates

<p>Beta-D-glucopyranose pentaacetate was photobrominated to give the 5-baromide from which 6-deoxy-Beta-D-xylo-hex-5-enopyranose tetraacetate was obtained by reductive elimination. This reaction sequence represents an efficient new route to the 5-ene. A detailed investigation into the photobromination of Beta-D-glucopyranose pentaacetate with bromine and with NBS led to the isolation of several by-products containing bromine substituents at C-1 and/or C-5; their reactions with zinc-acetic acid were studied, and the conformations. in solution of four alkenes derived from the 5-bromo compound were determined. 2,3,4-Triacylated 2,3,4,5-tetrahydroxycyclohexanones were Obtained by mercury (II) catalysed rearrangement of 5-deoxyhex-5-enopyranose esters. The mechanism of this rearrangement, and some enopyranose esters The mechanism of this rearrangement, reactions of the products were examined. The use of these new carbocyclic compounds in the synthesis of branched-chain cyclitol derivatives was explored. By means of diazomethane or, alternatively, hydrogen cyanide, substituted cyclohexanes with one-carbon branches and tertiary hydroxyl groups at the site of chain-branching were preared. Attempts to eliminate water from these tertiary alcohols to give substituted cyclohexene-carbonitriles or -carbaldehydes were unsuccessful.</p>

Geospallins A–C: New Thiodiketopiperazines with Inhibitory Activity against Angiotensin-Converting Enzyme from a Deep-Sea-Derived Fungus Geosmithia pallida FS140

Three new thiodiketopiperazines, geospallins A–C (1–3), together with nine known analogues (4–12), were isolated from the culture of the deep-sea sediment-derived fungus Geosmithia pallida FS140. Among them, geospallins A and B (1 and 2) represent rare examples of thiodiketopiperazines featuring an S-methyl group at C-10 and a tertiary hydroxyl group at C-11. Their structures were determined by high-resolution electrospray mass spectrometry (HRESIMS), spectroscopic analyses, and electronic circular dichroism (ECD) calculations. Their angiotensin-converting enzyme (ACE) inhibitory activity was reported, and geospallins A–C (1–3) showed inhibitory activity with IC50 values of 29–35 µM.

Crystal structure of (20S)-21-[4-(2-hydroxypropan-2-yl)-1H-1,2,3-triazol-4-yl]-20-(4-methylpentyl)-5-pregnen-3β-ol with an unknown solvate

In the title cholesterol analogue, [systematic name: (3S,8S,9S,10R,13S,14S,17R)-17-{(S)-1-[4-(2-hydroxypropan-2-yl)-1H-1,2,3-triazol-1-yl]-6-methylheptan-2-yl}-10,13-dimethyl-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-3-ol] C32H53N3O2, a new chain, including an intermediate triazole and a tertiary hydroxyl group in the terminal position, has been added at position 20 inducing a change in its stereochemistry. In the crystal, molecules are linked by O—H...O and O—H...N hydrogen bonds, forming layers lying parallel to (-201) and enclosing R 4 4(36) ring motifs. The isopropyl group is disordered about two positions with a refined occupancy ratio of 0.763 (5):0.237 (5). A region of disordered electron density was corrected for using the SQUEEZE routine in PLATON (Spek (2015). Acta Cryst. C71, 9–18). The given chemical formula and other crystal data do not take into account the unknown solvent molecule(s).

Isopropylmagnesium chloride-promoted unilateral addition of Grignard reagents to β-diketones: one-pot syntheses of β-tertiary hydroxyl ketones or 3-substituted cyclic-2-enones

Regioselective unilateral additions of Grignards to acyclic or cyclic β-diketones were effectively promoted by sub-stoichiometric amounts of i-PrMgCl to afford β-tertiary alcohol ketones or 3-substituted cyclic-2-enones, respectively.