2.2.1. Synthesis of 2,2,5-trimethyl-1,3-dioxolan-4-one (LA-Me,Me)

For the synthesis of LA-Me,Me, we followed the procedure reported by Miyagawa et al. [42] with the following modifications.

We used 45.0 g of DL-lactic acid (0.500 mol), 300 mL of a solution 1:1 v/v acetone (2.00 mol) and petroleum ether (bp: 60–80 ◦C), and 1.42 g of *p*TsOH (7.50 mmol) as a Brønsted acid catalyst were added in a 500 mL round-bottom flask equipped with a 25 mL Dean–Stark trap and Allihn condenser.

The reaction mixture was refluxed for 24 h under magnetic stirring. After reaction time, the crude mixture was placed in an ice bath and treated with 3.0 g of Na2CO3 (35 mmol) for 30 min. The reaction crude was filtered, and volatile solvent evaporated under reduced pressure. The product was isolated by vacuum distillation (15 mbar) at 50–52 ◦C. 1H NMR (400 MHz, CDCl3) δ 4.46 (q, J = 6.8 Hz, 1H), 1.59 (s, 3H), 1.52 (s, 3H), 1.46 (d, J = 6.8 Hz, 3H).

#### 2.2.2. Synthesis of 2,5-dimetil-1,3-dioxolan-4-one (LA-Me,H)

For the synthesis of LA-Me,H, we followed the procedure reported by Okada et al. [43] with the following modifications.

Here, 45.0 g of DL-lactic acid (0.500 mol), 32.0 mL of paraldehyde (0.250 mol), 650 mL of petroleum ether (bp: 60–80 ◦C) and 3.65 g of Amberlite® IR-120 (H<sup>+</sup> form) as heterogeneous Brønsted acid catalyst were added in a 1000 mL round-bottom flask equipped with a 25 mL

Dean–Stark trap and Allihn condenser. The reaction was refluxed under magnetic stirring for 5 h. Crude mixture was cooled at room temperature and filtered to remove the catalyst. The volatile solvent was removed, and the product was isolated by vacuum distillation (15 mbar) at 47–49 ◦C. The product resulted as a mixture of cis-trans stereoisomers in a 70:30 ratio. Major stereoisomer: 1H NMR (400 MHz, CDCl3) δ 5.64 (q, 1H, J = 5.0 Hz), 4.35 (q, 1H, J = 7.0 Hz).1.59 (d, 3H, J = 5.0 Hz), 1.52 (d, 3H, J = 7.0 Hz). Minor stereoisomer: 1H NMR (400 MHz, CDCl3) δ 5.84 (q, 1H, J = 5.0 Hz), 4.50 (q, 1H, J = 7.0 Hz), 1.55 (d, 3H, J = 5.0 Hz), 1.48 (d, 3H, J = 7.0 Hz).
