Compound 18
2,2'-((2R,3R,4S,5R,6S,7S,8R,9S,10R,11R)-3,4,5,6,7,8,9,10-octamethyldodecane-2,11-diyl)bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolane)
From: Odd–even alternations in helical propensity of a homologous series of hydrocarbons
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InChIKey NPQRKXAFXLOQRL-ICHGTFGISA-N
Compound data: NMR
Compound data: Crystallographic data
Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.
Boronic ester 14 (75 mg, 0.20 mmol, 1.00 eq.) was homologated with stannane (S)-11, (R)-11 and (S)-11 (207 mg, 0.47 mmol, 2.30 eq.), and n-BuLi (1.54 M in n-hexane, 0.31 mL, 0.47 mmol, 2.30 eq.) according to GP2 outlined for compound 14. The crude residue was purified by flash column chromatography (n-pentane:Et2O 99:1) to give 18 (82 mg, 75% over 3 steps) as a crystalline white solid. . TLC: Rf = 0.32 (n-pentane:Et2O 95:5). m.p.: 179 – 181 °C (n-hexane). 1H NMR: (500 MHz, Chloroform-d) δ 1.70 (2H, dqd, J = 8.6, 6.8, 4.5 Hz, H5), 1.54 (2H, m, H11), 1.47 (2H, dqd, J = 7.7, 6.7, 3.7 Hz, H9), 1.32 (2H, dqd, J = 7.7, 6.8, 4.5 Hz, H7), 1.23 (12H, s, H1), 1.23 (12H, s, H1’), 1.05 (2H, dq, J = 8.6, 7.3 Hz, H3), 0.91 (6H, d, J = 7.3 Hz, H4), 0.75 (6H, d, J = 6.8 Hz, H6), 0.73 (12H, d, J = 6.8 Hz, H8 & H12), 0.69 (6H, d, J = 6.7 Hz, H10) ppm. 13C NMR: (126 MHz, Chloroform-d) δ 82.8 (C2), 39.5 (C7), 35.8 (C5 or C9), 35.8 (C9 or C5), 35.3 (C11), 25.1 (C1), 24.7 (C1’), 21.7 (C3), 13.0 (C6), 12.7 (C4), 12.1 (CH3), 12.0 (CH3), 11.9 (CH3) ppm. HRMS (m/z): (ESI+) calc’d for C32H64B2NaO4 [M+Na]+: 557.4894; found: 557.4886. IR (νmax): 2970, 1452, 1362, 1307, 1204, 1146, 1076, 967, 855, 702 cm−1. [α]D22: +12 (CHCl3, c = 1.0).
