Easy Access to Aroma Active Unsaturated γ-Lactones by Addition of Modified Titanium Homoenolate to Aldehydes

Abstract

The homo-Reformatsky reaction, in which a metal homoenolate of an ester is added to an aldehyde, was adapted to produce γ-lactones from unsaturated, enolizable aldehydes. By use of titanium homoenolate, 11 different γ-lactones were synthesized in one step with moderate to good yields from readily available aldehydes. In particular, this procedure allowed the rapid preparation of a series of C(12) unsaturated γ-lactones differing in the position and configuration of the double bond. These reference compounds will be used to identify previously unknown lactones in butter oil. The chromatographic, spectral, and sensory descriptions of the synthesized lactones are provided.

Volatile Composition of Oyster Leaf (Mertensia maritima (L.) Gray)

“…After absorption of 870 mL, the reaction mixture was filtered and concentrated. Bulb-to-bulb distillation afforded 117 in a 96% yield: bp, 73 °C/0.25 mbar; IR, 3412, 3011, 2963, 2933, 2874, 1654, 1462, 1403, 1374, 1309, 1282, 1209, 1079, 1023, 977, 940, 908, 858, 814, 794, 719, 640; 1 H NMR, δ 0.97 (t, J = 7.7 Hz, 3H); 2.05 (quint, J = 7.7 Hz, 2H); 2.28−2.44 (m, 3H); 2.95− 3.01 (m, 2H); 3.61 (dd, J = 4.5, 12.8 Hz, 1H); 3.90 (dd, J = 2.5, 12.8 Hz, 1H); 5.32−5.39 (m, 1H); 5.50−5.58 (m, 1H); 13 C NMR, δ 14.2 (q); 20.7 (t); 29.2 (t); 55.3 (d); 58.2 (d); 61.7 (t); 122.3 (d); 134.9 (d); MS (EI, 70 eV), 142 (0, M +• ); 127 (1); 111 (15); 95 (16); 93 (17); 91 (10); 83 (21); 82 (35); 81 (40); 79 (22); 77 (10); 69 (38); 68 (45); 67 (100); 65 (10); 61 (12); 57 (23); 56 (11); 55 (68); 54 (18); 53 (21); 43 (31); 41 (75); 39 (32).…”

“…( Z , Z )-3,6-Nonadienal 64 was prepared as described by Frerot et al: MS (EI, 70 eV), m / z (%) 138 (6); 123 (12); 110 (11); 109 (20); 95 (30); 94 (13); 84 (29); 82 (20); 81 (35); 79 (44); 70 (30); 69 (29); 68 (23); 67 (100); 55 (60); 53 (24); 41 (90).…”

“…To confirm the presence of ( Z )-3-nonenal in the extract, ( E )-3-nonenal was prepared with 99% purity by GC-MS, as described in Frerot et al, and was reinjected for MS and LRI comparison: MS (EI, 70 eV), m / z (%) 140 (1); 122 (4); 111 (6); 98 (16); 97 (15); 96 (28); 85 (12); 84 (56); 83 (51); 81 (24); 70 (41); 69 (83); 67 (25); 57 (26); 56 (25); 55 (100); 54 (25); 41 (86). LRI (SPB-1) 1075; LRI (SWax) 1447.…”

Selective Carbon–Carbon Bond Cleavage of Cyclopropanols

“…9,95,102 Frerot and co-workers have found that a homoaldol and cyclization protocol can generate γ-lactones in one pot. 103 Their scope of lactone products was aroma-active, and the products were evaluated by taste by four expert flavorists at Firmenich SA to determine the compounds' flavor profile.…”

Discovery of New Lactones in Sweet Cream Butter Oil

“…All these spectral data were in accordance with γ-dodecalactones bearing a double bond in the side chain, namely n -dodecen-4-olides. The addition of titanium enolate to unsaturated aldehydes was used to prepare many dodecen-4-olides . The reference compounds were then used to establish the structure and double bond configuration of the naturally occurring lactones (unknowns 1–6 ) shown in Figure and Table .…”