Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
  • C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
  • C07C37/86—Purification; separation; Use of additives, e.g. for stabilisation by treatment giving rise to a chemical modification
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
  • C07C41/01—Preparation of ethers
  • C07C41/34—Separation; Purification; Stabilisation; Use of additives
  • C07C41/44—Separation; Purification; Stabilisation; Use of additives by treatments giving rise to a chemical modification
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
  • C07B2200/00—Indexing scheme relating to specific properties of organic compounds
  • C07B2200/07—Optical isomers
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2603/00—Systems containing at least three condensed rings
  • C07C2603/93—Spiro compounds
  • C07C2603/94—Spiro compounds containing "free" spiro atoms

Definitions

• the present invention involves the chemical separation of enantiomers of l,r-spirobiindane-6,6'-diol derivatives.
• This methodology employs (1) the preparation of achiral esters of the racemic l,r-spirobiindane-6,6'-diol derivatives, (2) the enantio-selective enzymatic hydrolysis of these racemic mixtures and (3) the eventual isolation of substantially enantiomerically enriched samples of the requisite 1,1'- spirobiindane-6,6'-diol derivatives after achiral chromatographic purification. While this technology has been demonstrated to be useful in the preparation of hundreds of grams of nonracemic 1 , 1 '-spirobiindane-6,6'-diol derivatives, it suffers from substantial drawbacks.
• the initial step of Kazlauskas resolution requires the synthetic preparation of ester derivatives of the racemic 1,1'- spirobiindane-6,6'-diol. This material is then exposed to an appropriate enzyme formulation in aqueous media for several days. During this reaction phase, care must be taken to control reaction temperature and solution alkalinity. Careful analysis of reaction composition is also needed to alter reaction conditions, thus ensuring optimal conversion to nonracemic product. With the completion of the enzymatic reaction, multiple solvent extractions provide a nonracemic residue that must be further purified. Achiral silica gel chromatography, employing the environmentally suspect methylene chloride as an eluant, then provides the nonracemic products.
• the requisite racemic spirobiindandiol substrate was reacted with a nonracemic chiral isocyanate to yield a mixture of diastereomeric mixture of urethane products.
• the mixture was then purified by repeated recrystallizations from benzene, a solvent designated a cancer suspect agent by the EPA.
• the desired spirobiindane was secured by chemical degradation of the chiral urethane groups.
• Esters of phenols in general are very commonly encountered organic compounds. Within this context, they are meant to include structurally those derived from a l,r-spirobiindane-6,6'-diol and a carboxylic acid component.
• the acid component can be alkyl, cycloalkyl, aryl, alkyloxy (alkylcarbonic acid), cycloalkyl (cycloalkylcarbonic acid), or aryloxy (arylcarbonic acid).
• General methods for the preparation of phenyl esters are apparent to those skilled in the art.
• reaction of the phenol with an acid chloride under basic conditions include: (1) reaction of the phenol with an acid chloride under basic conditions; (2) reaction of a phenol with a carboxylic acid under acidic conditions; (3) reaction of the phenol with a chloroformate; (4) reaction of a phenol and a carboxylic acid using a condensing agent; (5) reaction of the phenol with phosgene to prepare an intermediary phenyl chloroformate, that then can be condensed with a second phenol or alcohol, and similar transformations.
• a variety of nonracemic chiral carboxylic acids, acid chlorides, chloroformates, and alcohols are available for the preparation of esters of potential use in separating l,l'-spirobiindane-6,6'-diol enantiomers.
• These substrates may in turn be derived from natural sources, isolated chromatographically, prepared via enantio-selective methods, or otherwise purified. Most commonly, natural product derivatives are employed as
• the present invention relates to a method for the chemical separation of the enantiomers of l,r-spirobiindane-6,6'-diol derivatives comprising providing a racemic chiral l,r-spirobiindane-6,6'-diol derivative, reacting a nonracemic chiral component with the racemic chiral 1,1'- spirobiindane-6,6'-diol derivative to afford a mixture of diastereomeric diesters, separating the mixture of diastereomeric diesters to provide a substantially pure individual diastereomeric diester, and chemically removing the ester groups from the substantially pure individual diastereomeric diester to provide a nonracemic chiral 1,1 '-spirobiindane-6,6'-diol derivative.
• the present invention includes several advantages, not all of which are incorporated in a single embodiment.
• This method is shown to avoid the need for long chemical reaction times, carefully controlled reaction conditions, detailed reaction analyses, chromatographic separations, and the use of chlorinated solvents.
• This method is a simple reaction/separation sequence affording chiral resolution of spirobiindanediols of use in preparing novel chiral dopants and other high value materials.
• the present invention relates to a novel method for the chemical separation of the enantiomers of l,r-spirobiindane-6,6'-diol derivatives.
• This method includes formation of chiral, nonracemic esters from the racemic 1,1'- spirobiindane-6,6'-diol derivatives, the separation of the so-derived mixture to provide nonracemic diastereomeric components, and finally, chemical removal of the appended ester groups to provide resolved enantiomerically enriched 1,1'- spirobiindane-6,6'-diol derivatives.
• racemic l,r-spirobiindane-6,6'-diol derivatives can be obtained by means of known synthetic procedures or less likely from commercial sources.
• Such compounds useful in this process are generally described by compounds of Structure 2, wherein R 1 , R 2 , R 3 , and R 4 are independently hydrogen, or any carbon substituents, X groups are independently any substituent, and n are independently an integer 0-3 and wherein these substituents may for a ring.
• all of the R 1 , R 2 , R 3 , and R 4 are hydrogen or lower alkyl group to include groups containing one to about eight carbon atoms, e.g.
• the racemic l,r-spirobiindane-6,6'-diol is then suitably reacted with a chiral nonracemic component to form a mixture of diastereomeric diesters, that differ only in the configuration of the spiro-fused, stereogenic center.
• Suitable esters are described by Structure 3, wherein all of the substituents, save R E , are described as in Structure 2.
• the two RE groups are the same.
• the requisite diastereomer mixtures are prepared via condensation of the racemic l,r-spirobiindane-6,6'-diol directly with the nonracemic chiral acid component or with a suitably activated acid component usually in an organic solvent.
• activated acid components include carboxylic acid chlorides, carboxylic acid bromides, chloroformates, carboxylic acid anhydrides, mixed carboxylic acid-sulfonic acid anhydrides, bromoformates, mixed carbonic acid- sulfonic acid anhydrides.
• Direct condensations of racemic l,l'-spirobiindane-6,6'-diol derivatives with nonracemic chiral acids can be induced via strong acids or using condensing agents.
• Strong acids may include minerals acids such as sulfuric acid, phosphoric acid, hydrochloric acid or organic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, toluenesulfonic acid, or protic acids of similar acid strength.
• Condensing agents may include dicyclohexylcarbodiimide, diisopropylcarbodiimide, diethyl azodicarboxylate/triphenylphosphine, diisopropyl azodicarboxylate/triphenylphosphine, and similar reagents.
• racemic l,r-spirobiindane-6,6'-diol derivatives may be converted to their corresponding bis-chloroformate, then condensed with suitable nonracemic alcohols under basic conditions to provide the desired mixture of diastereomeric diesters.
• suitable nonracemic alcohols under basic conditions.
• phosgene or a phosgene equivalent such as trichloromethyl chloroformate (diphosgene) or bis- trichloromethyl carbonate (triphosgene)
• the so produced racemic bis-chloroformates they may be reacted with suitable nonracemic alcohols, under basic conditions, to provide the desired mixture of diastereomeric bis-carbonates.
• Typical alternative solvents include tetrahydrofuran (THF), dioxane, isopropyl ether (IPE), 1,2-dimethoxyethane (DME), ethyl acetate, propyl acetate, butyl acetate, acetonitrile, propionitrile, butyronitrile, toluene, xylenes, heptanes, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N-methylpyrrolidone (NMP), pyridine, or mixtures of such solvents.
• THF tetrahydrofuran
• dioxane isopropyl ether
• DIPE isopropyl ether
• DME 1,2-dimethoxyethane
• ethyl acetate propyl acetate
• butyl acetate acetonitrile
• propionitrile propionitrile
• Bases useful in the reactions of the invention include organic bases such as triethylamine, pyridine, diisopropylethylamine, 1,1,3,3- tetramethylguanadine, l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), dicyclohexylamine, and inorganic bases such as sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, potassium phosphate, cesium carbonate, sodium acetate.
• organic bases such as triethylamine, pyridine, diisopropylethylamine, 1,1,3,3- tetramethylguanadine, l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), dicyclohexylamine
• inorganic bases such as sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, potassium phosphate, cesium carbonate, sodium acetate.
• the suitably prepared mixture of diastereomeric diesters then can be separated via one of a variety of techniques known to those practiced in the art. These methods include trituration, in this case defined as stirring the material of interest with a designated organic liquid so as to induce crystallization, dissolve impurities, or allow break-up of a crystalline mass, fractional crystallization, recrystallization, achiral chromatography, high performance (or pressure) liquid chromatography (HPLC), flash chromatography.
• the separation of the diastereomeric esters proceeds via trituration of the mixture with a suitable organic solvent to induce crystallization of one diastereomeric diester, followed by filtration of the solid and drying of the crystallized diastereomeric diester.
• ester groups pendant on the core of the nonracemic l,r-spirobiindane-6,6'-diol diastereomeric diester are removed to provide the desired nonracemic l,l'-spirobiindane-6,6'-diol enantiomers.
• ester removal Many methods for such ester removal are known to those practiced in the art. Of particular note are hydrolyses under strongly acid or basic aqueous conditions, transesterification usually employing acidic reagents, nucleophilic displacements, ester reductions, and similar methods.
• Hydrolytic conditions usually entail reaction of the ester with bases, (for example, lithium hydroxide, sodium hydroxide, potassium hydroxide or cesium hydroxide) or mineral acid (for example, sulfuric acid, phosphoric acid, hydrochloric acid) in water or mixed water/solvent reaction media.
• bases for example, lithium hydroxide, sodium hydroxide, potassium hydroxide or cesium hydroxide
• mineral acid for example, sulfuric acid, phosphoric acid, hydrochloric acid
• Suitable solvents include methanol, ethanol, 2- propanol, 1-propanol, THF, DMF, DMA, NMP, DME, ethylene glycol or mixtures of these solvents.
• Transesterifications would usually involve reaction of the bis-ester with an excess of alcohol under acidic conditions, such that a nonracemic l,r-spirobiindane-6,6'-diol bis-ester would transfer its acid components to the hydroxylic solvent producing a new chiral esters and the nonracemic l,l'-spirobiindane-6,6'-diol derivative.
• Suitable hydroxylic solvents include methanol, ethanol, 2-propanol, 1-propanol, ethylene glycol.
• a suitable co-solvent may be added to improve reactant solubility.
• Step 2 Preparation of Diastereomeric Diester Mixture: A solution of ( ⁇ )-I-l (12.3 g; 40 mmol), triethylamine (TEA; 20 mL, 144 mmol), and 4-dimethylaminopyridine (DMAP; 1 g, 8 mmol) in 200 mL methylene chloride was treated over circa ten minutes with a solution of (-)- menthyl chloro formate ⁇ i.e. the chloroformate derived from (-)-menthol; CAS 14602-86-9; 18 mL, 84 mmol) in 5 mL methylene chloride.
• TSA triethylamine
• DMAP 4-dimethylaminopyridine
• the glassy residue containing an equimolar mixture of the diastereomeric diesters Int-2 and Int-3 as assessed by proton NMR spectroscopy, was dissolved in 150 mL heptanes. Shortly, crystallization initiated and the slurry stirred at ambient temperature for twenty hours. The slurry was chilled in an ice water bath then filtered; the solids washed with minimal cold heptanes and low- boiling ligroin to provide Int-2 as a colorless solid, 9.46 g (35 %; 70% based on single diastereomeric diester). This material proved chromatically homogenous and displayed spectral characteristics consistent with its assigned structure. High field NMR detected none of the alternative diastereomeric diester, Int-3.
• Step 3 Separation of Diastereomeric Diester Mixture
• (+)-I-l A second run (1.6X the original scale) of the preparation of (+)-I-l was accomplished as in Example 1, except the crude reaction product was not chromatographed, but rather triturated with isopropyl ether to provide (+)-I-l as a colorless solid (5.46g, 85%). This material proved chromatically homogenous and displayed spectral characteristics consistent with its assigned structure.
• Step 2 Preparation of Diastereomeric Diester Mixture: Another run (1.4X the original scale) of the chiral resolution of ( ⁇ )-
• Step 3 Separation of Diastereomeric Diester Mixture
• Step 4 Removal of Ester Groups - Hydrazine Method A solution of Int-9 (0.35 g, 0.57 mmol) in 7.5 mL THF was treated with hydrazine monohydrate (0.25 mL, 5.2 mmol) then heated at reflux for thirty minutes.

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• 2004
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