(S,E)-Methyl 2-((R)-4-methyl-1,2-dihydronaphthalen-2-yl)-4-phenylbut-3-enoate could be produced through the following synthetic routes.

A. 2-Carboxyethyltriphenylphosphonium chloride (CAS NO.: ). 3-Chloropropionic acid (16.3 g, 150 mmol) and triphenylphosphine (43.3 g, 165 mmol, 1.1 equiv) are added to a 250-mL, round-bottomed flask equipped with a magnetic stir bar. s (75 mL) are added and a water-cooled condenser is attached to the flask. Vigorous stirring is commenced and the solution is heated to reflux in an oil bath for 3 h during which time two layers form. The flask is then removed from the oil bath and the flask is fitted with a thermometer. When the solution has cooled to 60–70 °C, the thermometer is removed and acetonitrile (50 mL) is slowly added with vigorous stirring and scraping using a metal spatula to prevent the product from sticking to the sides of the flask. The product, which is eventually converted to a white solid, is collected by vacuum filtration in a Büchner funnel. The product is washed with diethyl ether (300 mL) and then dried under vacuum (0.05 mmHg) for 2 h to afford 46.6–46.7g (84%) of pure 2-carboxyethyltriphenylphosphonium chloride as a white solid.

B. 1-Methyl-3,4-dihydronaphthalene (CAS NO.: ). A 500-mL, 3-necked round-bottomed flask equipped with a stir bar is fitted with an argon inlet adaptor, a 100-mL pressure-equalized addition funnel and a reflux condenser. The tops of the addition funnel and reflux condenser are sealed with septa, the apparatus is flame dried under vacuum (0.05 mmHg) and then is backfilled with argon. turnings (3.65 g, 150 mmol, 1.50 equiv) are then added and the flask is evacuated and filled with argon twice. Dry diethyl ether (100 mL) (Note 9) is added through the condenser via cannula. Iodomethane (9.98 mL, 22.7 g, 160 mmol, 1.60 equiv) is then added by syringe to the addition funnel. Stirring is commenced and the iodomethane is added dropwise to the magnesium turnings at a rate sufficient to maintain a gentle reflux (13–17 min is required to complete the addition). The solution is then stirred for another 20 min after the addition is complete. A solution of α-tetralone (14.6 g, 100 mmol) in dry diethyl ether (10 mL) is transferred via syringe from a flame-dried 100-mL round bottom flask to the addition funnel and then added dropwise to the methyl magnesium iodide solution at a rate sufficient to maintain a gentle reflux (12–16 min is required for the addition). The solution is stirred for another 15 min after completion of the addition. The rubber septa are then removed from the tops of both the condenser and the addition funnel. An aqueous solution of 3 N HCl (60 mL) is placed in the addition funnel and then is added dropwise to the solution over 30 min. The mixture is then vigorously stirred for 1 h at room temperature, after which time the mixture is poured into a 250-mL separatory funnel and the layers are separated. The aqueous layer is extracted with diethyl ether (3 × 30 mL). The combined ether extracts are washed with brine (50 mL), dried over anhydrous MgSO₄, vacuum filtered through a plug of silica gel (24 g) in a Büchner funnel and then concentrated by rotary evaporation at room temperature. The residue is purified by flash column chromatography on 130 g of silica gel eluting with pentane (450 mL). The fractions containing product are collected and concentrated by rotary evaporation (11 mmHg, room temperature) to afford 13.1–13.2 g (91–92%) of pure 1-methyl-3,4-dihydronaphthalene as a clear oil.

C. (E)-Methyl 2-diazo-4-phenylbut-3-enoate (CAS NO.: ). 2-Carboxyethyl-triphenylphosphonium chloride (26.7 g, 72.0 mmol, 1.20 equiv) is added to a flame-dried, 2-necked 500-mL, round-bottomed flask equipped with a magnetic stir bar and fitted with a rubber septum and an argon inlet adaptor. The flask is evacuated (0.05 mmHg) and filled with argon two times after which a positive argon pressure is maintained on the flask. (6.07 mL, 6.37 g, 60.0 mmol) and THF (130 mL) are then added by syringe and the flask is externally cooled to 0 °C in an ice-water bath and vigorous stirring is begun. A solution of potassium tert-butoxide (16.8 g, 150 mmol, 2.5 equiv) in THF (80 mL) under an argon atmosphere and at 0 °C is then added via cannula under positive argon pressure over 30 min. After the addition is complete, the solution is stirred at 0 °C for 30 min, then the ice-water bath is removed and stirring is continued for another 20 min. (11.4 mL, 15.1 g, 120 mmol, 2.0 equiv) is then added rapidly by syringe and stirring is continued at ambient temperature for 2.5 h. The septum is then briefly removed from the flask and para-acetamidobenzenesulfonyl azide (18.7 g, 78.0 mmol, 1.30 equiv) is added in one portion. The septum is replaced and the flask, under a positive argon pressure, is externally cooled to 0 °C in an ice-water bath. (11.7 mL, 11.9 g, 78.0 mmol) is then added rapidly by syringe and the solution quickly becomes red. Stirring is continued at 0 °C for 4 h and then the solution is allowed to warm to room temperature and then is transferred to a 1-L, single-necked, round-bottomed flask and the solution is concentrated by rotary evaporation (27 mmHg, ambient temperature). The residue is treated with saturated aqueous ammonium chloride solution (150 mL) and diethyl ether (400 mL) and the mixture is poured into a 1-L separatory funnel and vigorously shaken. The aqueous layer is drained and the organic layer is washed with saturated ammonium chloride solution (150 mL) and then is dried over anhydrous MgSO₄ (5 g). The solvent is removed by rotary evaporation (11 mmHg, room temperature) to give a dark-red oil. The oil is then adsorbed onto 50 g of silica gel, which is then placed at the top of a packed column of silica gel (350 g). The column is eluted with pentanes/diethyl ether, 12:1. The red fractions containing the product are collected and concentrated by rotary evaporation at room temperature to afford 9.3–9.7 g (77–80%) of 1 as a red solid.

D. (S,E)-Methyl 2-((R)-4-methyl-1,2-dihydronaphthalen-2-yl)-4-phenylbut-3-enoate (CAS NO.: 76531-50-5). 1-Methyl-3,4-dihydronaphthalene (5.34 g, 37.0 mmol) and Rh₂(S-DOSP)₄ (7.0 mg, 0.0037 mmol, 0.0001 equiv) are added to a flame-dried, 250-mL 2-necked, round-bottomed flask equipped with a magnetic stir bar and fitted with an argon inlet adaptor and a rubber septum. The flask is evacuated (0.05 mmHg) and purged with argon twice and then maintained under a positive argon pressure. 2,2-Dimethylbutane (40 mL) is added by syringe and vigorous stirring is begun. A solution of (E)-methyl 2-diazo-4-phenylbut-3-enoate 1 (8.23 g, 40.7 mmol, 1.10 equiv) in 2,2-dimethylbutane (60 mL) is added by syringe pump over 4 h. The solution is stirred for an additional 10 h and the solvent is then removed by rotary evaporation (11 mmHg, room temperature) to give a light-yellow solid. Absolute ethanol (20 mL) is added to the crude material and a reflux condenser is attached to the flask. The solution is heated to reflux to dissolve the material and then allowed to cool to room temperature, whereupon the product crystallizes as an off-white solid. The solution is then cooled to 0 °C for 2 h and the product is collected by vacuum filtration on a Büchner funnel to give 8.0–8.3 g (68–70%) of pure 2 as an off-white solid.