(3S)-3-hydroxy-4,4-dimethyloxolan-2-one

Conditions: temp:80.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The aqueous phase (21 ml; Na L-pantoate) was adjusted to pH 1 with about 5 ml of 3 M H2SO4, heated at 80° C. for 15 min and mixed with 8 g of anhydrous Na2SO4. The resulting L-pantolactone was analogously extracted 3× with one volume of ethyl acetate, dried with Na2SO4 and evaporated. For recycling to the hydrolysis, the L-pantolactone melt can be racemized by heating after addition of NaOH in the presence of small amounts of Na L-pantoate (180° C., 3 h). The resulting L-pantolactone was analogously extracted 3× with one volume of ethyl acetate dried with Na2SO4 evaporated For recycling to the hydrolysis by heating

Conditions: temp:80.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The aqueous phase (21 ml; Na L-pantoate) was adjusted to pH 1 with about 5 ml of 3 M H2SO4, heated at 80° C. for 15 min and mixed with 8 g of anhydrous Na2SO4. The resulting L-pantolactone was analogously extracted 3× with one volume of ethyl acetate, dried with Na2SO4 and evaporated. For recycling to the hydrolysis, the L-pantolactone melt can be racemized by heating after addition of NaOH in the presence of small amounts of Na L-pantoate (180° C., 3 h). The resulting L-pantolactone was analogously extracted 3× with one volume of ethyl acetate dried with Na2SO4 evaporated For recycling to the hydrolysis by heating

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A full inoculating loop of E. coli XL1Blue pKS+681 was grown (overnight, 37° C.) on an LB plate with ampicillin (100 μg/ml), IPTG (0.2 mM) and X-Gal (80 mg/l) and then resuspended (OD600=2.5) in 0.5 ml of Tris-HCl pH 7.0 and 50 mM D,L-pantolactone. A corresponding E. coli XL1Blue pBluescriptKS+-sample (OD600=2.5) was a useful comparison. After 1 h, the cells were centrifuged down and D,L-pantolactone, D,L-, D-, and L-pantoic acid were determined by HPLC analysis. Tab. 6a shows the activities and ee values for the various samples. The suspension had an activity of >90 U/L. However, no significant activity was evident in liquid culture batches (cf. Example 12). (overnight, 37° C.)

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a 0° C. solution of 5.01 g (38.5 mmol) of (S)-(+)-pantolactone in 150 mL of methanol was carefully added 3.72 g (98.5 mmol) of sodium borohydride. After gas evolution had subsided, the ice-bath was removed and the reaction closely monitored, cooling to 0° C. with an ice-water bath as needed when gas evolution became vigorous. The ice-water bath was removed and the reaction mixture was stirred at room temperature for 4 h. Dowex 50W×4-400 (H+) resin was added to the solution until a pH of 7 was achieved, as indicated by wet pH paper. The resin was filtered off, and the filtrate was evaporated under reduced pressure. Portions of methanol and toluene were distilled from the resulting oil, which was further dried under high vacuum to afford 5.16 g (quantitative yield) of (2S)-3,3-dimethyl-1,2,4-butanetriol. 1H NMR (300 MHz, CDCl3) δ 3.49-3.82 (m, 5H), 3.11 (d, J=4 Hz, 1H), 2.62 (m, 1H), 2.42 (m, 1H), 0.98 (d, J=6 Hz, 6H). To a 0° C. the ice-bath was removed the reaction The ice-water bath was removed Dowex 50W×4-400 (H+) resin was added to the solution until a pH of 7 The resin was filtered off the filtrate was evaporated under reduced pressure Portions of methanol and toluene were distilled from the resulting oil, which was further dried under high vacuum

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a 0° C. solution of 5.01 g (38.5 mmol) of (S)-(+)-pantolactone in 150 mL of methanol was carefully added 3.72 g (98.5 mmol) of sodium borohydride. After gas evolution had subsided, the ice-bath was removed and the reaction closely monitored, cooling to 0° C. with an ice-water bath as needed when gas evolution became vigorous. The ice-water bath was removed and the reaction mixture was stirred at room temperature for 4 h. Dowex 50W×4-400 (H+) resin was added to the solution until a pH of 7 was achieved, as indicated by wet pH paper. The resin was filtered off, and the filtrate was evaporated under reduced pressure. Portions of methanol and toluene were distilled from the resulting oil, which was further dried under high vacuum to afford 5.16 g (quantitative yield) of (2S)-3,3-dimethyl-1,2,4-butanetriol. 1H NMR (300 MHz, CDCl3) δ 3.49-3.82 (m, 5H), 3.11 (d, J=4 Hz, 1H), 2.62 (m, 1H), 2.42 (m, 1H), 0.98 (d, J=6 Hz, 6H). To a 0° C. the ice-bath was removed the reaction The ice-water bath was removed Dowex 50W×4-400 (H+) resin was added to the solution until a pH of 7 The resin was filtered off the filtrate was evaporated under reduced pressure Portions of methanol and toluene were distilled from the resulting oil, which was further dried under high vacuum

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Phosgene (1.04 mL, 1.93 M, 2.00 mmol) was added dropwise to a solution of (S)-(+)-pantolactone (130 mg, 1.00 mmol) and quinoline (0.241 mL, 2.00 mmol) in anhydrous tetrahydrofuran (3 mL) at 0° C. under nitrogen. The cold bath was removed, and the mixture was stirred for 18 h at room temperature. Volatiles were then removed under vacuum, and the resulting solid was slurried in anhydrous tetrahydrofuran (4 mL) under nitrogen. A solution of triethylamine (0.153 mL, 1.10 mmol) and (3S)-3-amino-2-hydroxy-N-[(1R)-1-phenylethyl]heptanamide (264 mg, 1.00 mmol) in anhydrous tetrahydrofuran was added. The resulting mixture was stirred for 18 h, and was then partitioned between ethyl acetate (70 mL) and 1 N hydrochloric acid (35 mL). The ethyl acetate layer was washed further with two 35 mL portions of 1 N hydrochloric acid, followed by saturated aqueous sodium chloride (35 mL). After drying over magnesium sulfate, volatiles were removed to afford (3S)-4,4-dimethyl-2-oxotetrahydro-3-furanyl (1S)-1-(1-hydroxy-2-oxo-2-{[(1R)-1-phenylethyl]amino}ethyl)pentylcarbamate as a tan oil (358 mg, 85%). The cold bath was removed Volatiles were then removed under vacuum The resulting mixture was stirred for 18 h was then partitioned between ethyl acetate (70 mL) and 1 N hydrochloric acid (35 mL) The ethyl acetate layer was washed further with two 35 mL portions of 1 N hydrochloric acid After drying over magnesium sulfate, volatiles were removed

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Phosgene (1.04 mL, 1.93 M, 2.00 mmol) was added dropwise to a solution of (S)-(+)-pantolactone (130 mg, 1.00 mmol) and quinoline (0.241 mL, 2.00 mmol) in anhydrous tetrahydrofuran (3 mL) at 0° C. under nitrogen. The cold bath was removed, and the mixture was stirred for 18 h at room temperature. Volatiles were then removed under vacuum, and the resulting solid was slurried in anhydrous tetrahydrofuran (4 mL) under nitrogen. A solution of triethylamine (0.153 mL, 1.10 mmol) and (3S)-3-amino-2-hydroxy-N-[(1R)-1-phenylethyl]heptanamide (264 mg, 1.00 mmol) in anhydrous tetrahydrofuran was added. The resulting mixture was stirred for 18 h, and was then partitioned between ethyl acetate (70 mL) and 1 N hydrochloric acid (35 mL). The ethyl acetate layer was washed further with two 35 mL portions of 1 N hydrochloric acid, followed by saturated aqueous sodium chloride (35 mL). After drying over magnesium sulfate, volatiles were removed to afford (3S)-4,4-dimethyl-2-oxotetrahydro-3-furanyl (1S)-1-(1-hydroxy-2-oxo-2-{[(1R)-1-phenylethyl]amino}ethyl)pentylcarbamate as a tan oil (358 mg, 85%). The cold bath was removed Volatiles were then removed under vacuum The resulting mixture was stirred for 18 h was then partitioned between ethyl acetate (70 mL) and 1 N hydrochloric acid (35 mL) The ethyl acetate layer was washed further with two 35 mL portions of 1 N hydrochloric acid After drying over magnesium sulfate, volatiles were removed

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Acrylic acid 4,4-dimethyl-2-oxo-tetrahydro-furan-3-yl ester (R) was prepared in the following manner: 3-(S)-Hydroxy-4,4-dimethyl-dihydro-furan-2-one (2.60 g, 20 mmol) and diisopropylethylamine (5.2 mL, 30 mmol) in dichloromethane (25 mL) was cooled to −10° C. and treated dropwise with acryloyl chloride (2.03 mL, 25 mmol) and stirred for 2 h. 1M HCl (20 mL) was added and the organic layer was washed with sodium bicarbonate and water. The organic layer was dried over sodium sulfate, filtered and concentrated. Flash chromatography (10-40% EtOAc, hexanes) afforded 2.09 g (57% yield) of the desired acrylic acid 4,4-dimethyl-2-oxo-tetrahydro-furan-3-yl ester (R) as a clear oil. This substrate was used to prepare the acid chloride of (1R)-4-methyl-cyclohex-3-enecarboxylic acid analogous to the procedure described in Scheme 15 and Scheme 16. Acrylic acid 4,4-dimethyl-2-oxo-tetrahydro-furan-3-yl ester (R) was prepared in the following manner the organic layer was washed with sodium bicarbonate and water The organic layer was dried over sodium sulfate filtered concentrated

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Acrylic acid 4,4-dimethyl-2-oxo-tetrahydro-furan-3-yl ester (R) was prepared in the following manner: 3-(S)-Hydroxy-4,4-dimethyl-dihydro-furan-2-one (2.60 g, 20 mmol) and diisopropylethylamine (5.2 mL, 30 mmol) in dichloromethane (25 mL) was cooled to −10° C. and treated dropwise with acryloyl chloride (2.03 mL, 25 mmol) and stirred for 2 h. 1M HCl (20 mL) was added and the organic layer was washed with sodium bicarbonate and water. The organic layer was dried over sodium sulfate, filtered and concentrated. Flash chromatography (10-40% EtOAc, hexanes) afforded 2.09 g (57% yield) of the desired acrylic acid 4,4-dimethyl-2-oxo-tetrahydro-furan-3-yl ester (R) as a clear oil. This substrate was used to prepare the acid chloride of (1R)-4-methyl-cyclohex-3-enecarboxylic acid analogous to the procedure described in Scheme 15 and Scheme 16. Acrylic acid 4,4-dimethyl-2-oxo-tetrahydro-furan-3-yl ester (R) was prepared in the following manner the organic layer was washed with sodium bicarbonate and water The organic layer was dried over sodium sulfate filtered concentrated

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The optically active bases (+)- and (-)-3-aminomethylpinane prove astonishingly stable in the course of the various stages of the process. In none of them are measurable quantities of by-products produced, so that when recycling the (+)- or (-)-3-aminomethylpinane and L-pantolactone for re-use, neither the 3-aminomethylpinane nor the racemized pantolactone has to be subjected to special purification treatments. The optical purity of the D-pantolactone obtained in accordance with the process corresponds, within the limits of analytical error, to the data given in Example 3 for the product obtained from a first separation, even after the optically active base used, the racemized pantolactone left in each case, and the solvent used, have been recycled 20 times; this shows that special purification treatments are not necessary. The new process gives optically pure D-(-)-pantolactone in an overall yield of 90%, based on the DL-pantolactone employed. produced, so that when to be subjected to special purification treatments

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Adapting procedures or variations thereof according to O'Brien et al., Tetrahedron Lett. 2002, 43, 5491-5494; Weinges et al., Chem. Ber. 1994, 127, 1305-1309; Johnston et al., J. Chem. Soc. Perkin Trans. I, 2000, 5, 681-695; Iversen et al, J. Chem. Soc. Chem. Commun. 1981, 1240-1241; Wessel et al. J. Chem. Soc. Perkin Trans. I, 1985, 2247-2250; Enders et al., Org. Syntheses 2002, 78, 177-183; and Rai et al., Tetrahedron Lett. 2003, 44, 2267-2269, in a representative example, an oven-dried three necked 3,000 mL round bottomed flask equipped with a Tallboys 138 over-head mechanical stirrer was charged under a nitrogen atmosphere with 97.6-117.1 g (750-900 mmol, 1.25-1.5 mol-eq.) of D-pantolactone. The lactone was dissolved in a mixture of 700 mL of anhydrous cyclohexane (Chx) and 300 mL of anhydrous dichloromethane (DCM). One-hundred twelve (112) mL (151.5 g, 600 mmol) of commercially available O-benzyl 2,2,2-trichloroacetimidate or suitable derivative thereof such as O-(4-methoxybenzyl) 2,2,2-trichloroacetimidate was added and the solution cooled to ca. 0° C. (ice bath). Ca. 2.65 mL (ca. 4.50 g, ca. 30 mmol, ca. 5 mol-%) of anhydrous trifluoromethanesulfonic acid (triflic acid) was added dropwise to the stirred reaction mixture. (Caution: The O-benzylation reaction is exothermic!) Other useful catalyst systems include Brønstedt-acids such as para-toluenesulfonic acid (TsOH), camphorsulphonic acid (CSA), trifluoroacetic acid (TFA), and Lewis-acids such as trifluoroborane diethyl ether complex (BF3.Et2O), trityl tetrafluoroborate (TrBF4), trityl perchlorate (TrClO4), trimethylsilyl trifluoromethanesulfonate (TMSOTf), or tin- and lanthanide triflates (Sn(OTf)2, Ln(OTf)3 in similar or other suitable solvents such as toluene or acetonitrile. The reaction was stirred with gradual warming to room temperature for approximately 24 hours. The reaction was then quenched by addition of water and the reaction mixture was diluted with hexane (Hxn). The reaction mixture was stirred for an additional three hours to ensure hydrolysis of unreacted O-benzyl or (4-methoxybenzyl) 2,2,2-trichloroacetimidate. The reaction mixture was filtered to remove part of the precipitated 2,2,2-trichloroacetamide. After phase separation, the aqueous phase was extracted three more times with hexanes (Hxn), diethyl ether (Et2O), or other suitable solvent. The combined organic extracts were washed with a saturated aqueous solution of sodium hydrogen carbonate (NaHCO3), brine, and dried over anhydrous magnesium sulfate (MgSO4). After filtration and evaporation of the solvents under reduced pressure using a rotary evaporator, the O-protected D- or D/L-pantolactone was obtained as a yellow-brown to colorless, clear oil, typically of high chemical purity as determined by TLC and/or 1H NMR spectroscopy, that solidified upon refrigeration (4° C.). The material thus prepared was generally of sufficient purity to be used directly in the next step without further isolation or purification. Optionally, the isolated material was further purified by silica gel column chromatography using ethyl acetate (EtOAc) and hexane (Hxn) or n-heptane (Hptn) mixtures and/or gradients as eluent to provide O-protected D-pantolactone as a colorless, viscous oil or solid. O-protected D-pantolactone was also further purified by crystallization from pentane (Pnt), hexanes (Hxn), or n-heptane (Hptn) to provide colorless crystals. equipped with a Tallboys 138 over-head mechanical stirrer (Caution: The O-benzylation reaction with gradual warming to room temperature for approximately 24 hours The reaction was then quenched by addition of water the reaction mixture was diluted with hexane (Hxn) The reaction mixture was stirred for an additional three hours hydrolysis of unreacted O-benzyl or (4-methoxybenzyl) 2,2,2-trichloroacetimidate The reaction mixture was filtered to remove part of the precipitated 2,2,2-trichloroacetamide After phase separation the aqueous phase was extracted three more times with hexanes (Hxn), diethyl ether (Et2O), or other suitable solvent The combined organic extracts were washed with a saturated aqueous solution of sodium hydrogen carbonate (NaHCO3), brine dried over anhydrous magnesium sulfate (MgSO4) After filtration and evaporation of the solvents under reduced pressure a rotary evaporator

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Acrylic acid 4,4-dimethyl-2-oxo-tetrahydro-furan-3-yl ester (R) was prepared in the following manner: 3-(S)-Hydroxy-4,4-dimethyl-dihydro-furan-2-one (2.60 g, 20 mmol) and diisopropylethylamine (5.2 mL, 30 mmol) in dichloromethane (25 mL) was cooled to −10° C. and treated dropwise with acryloyl chloride (2.03 mL, 25 mmol) and stirred for 2 h. 1M HCl (20 mL) was added and the organic layer was washed with sodium bicarbonate and water. The organic layer was dried over sodium sulfate, filtered and concentrated. Flash chromatography (10-40% EtOAc, hexanes) afforded 2.09 g (57% yield) of the desired acrylic acid 4,4-dimethyl-2-oxo-tetrahydro-furan-3-yl ester (R) as a clear oil. This substrate was used to prepare the acid chloride of (1R)-4-methyl-cyclohex-3-enecarboxylic acid analogous to the procedure described in Scheme 15 and Scheme 16. Acrylic acid 4,4-dimethyl-2-oxo-tetrahydro-furan-3-yl ester (R) was prepared in the following manner the organic layer was washed with sodium bicarbonate and water The organic layer was dried over sodium sulfate filtered concentrated