Efficient Construction of the Carbon Skeleton of the Novel Polyoxazole-Based Cyclopeptide IB-01211 via a Biomimetic Macrocyclisation

Abstract

An efficient construction of the entire carbon skeleton of the novel polyoxazole-based natural product IB-01211 was developed which featured a biomimetic macrocyclisation of an ω-amino acid tethered through two bisoxazole units as the key step.

Key words

heterocycles - biomimetic - macrocyclisation - peptides - oxazoles

References and Notes

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16

All new compounds reported here gave satisfactory spectroscopic and/or analytical data.
Data for 27
Mp 144-146 ˚C. IR (KBr): 3367, 2927, 1683, 1652, 1515, 1259, 1114, 766 cm^-¹. ^¹H NMR (400 MHz, CDCl₃): δ = 9.46 (s, 1 H), 8.61 (d, J = 8.4 Hz, 1 H), 8.35 (s, 1 H), 8.27 (s, 1 H), 8.14 (s, 1 H), 8.13 (d, J = 7.2 Hz, 1 H), 7.64-7.62 (m, 2 H), 7.49-7.43 (m, 6 H), 7.40-7.38 (m, 4 H), 7.36-7.33 (m, 3 H), 6.88 (s, 1 H), 6.01 (dd, J = 6.8 Hz, 1 H), 5.97 (s, 1 H), 5.34-5.28 (m, 1 H), 4.63 (dd, J = 8.0, 4.8 Hz, 1 H), 4.10 (dd J = 9.2, 5.6 Hz, 1 H), 3.97-3.92 (m, 1 H), 3.73 (t J = 9.2 Hz, 1 H), 2.42-2.37 (m, 1 H), 1.90-1.87 (m, 1 H), 1.03-0.99 (m, 15 H), 0.90-0.86 (m, 2 H), 0.80 (d, J = 6.8 Hz, 3 H), 0.65 (t, J = 7.2 Hz, 3 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 171.7 (s), 169.9 (s), 164.5 (s), 160.3 (s), 159.1 (s), 158.6 (s), 154.6 (s), 152.1 (s), 151.6 (s), 141.8 (d), 139.3 (d), 139.1 (d), 137.3 (s), 135.0 (d), 134.9 (d), 132.7 (s), 132.6 (s), 132.2 (s), 131.8 (s), 130.4 (d), 130.3 (s), 129.9 (d), 129.8 (d), 129.5 (s), 128.5 (d), 128.3 (d), 127.8 (d), 127.7 (d), 126.0 (s), 105.2 (t), 64.7 (t), 59.8 (d), 56.4 (d), 49.3 (d), 38.2 (d), 29.2 (d), 26.3 (q), 24.7 (t), 19.8 (q), 18.7 (q), 18.3 (s), 14.9 (q), 11.1 (q). HRMS (TOFMS ES⁺): m/z [M⁺ + Na] calcd for C₅₁H₅₄N₈NaO₉Si: 973.3681; found: 973.3682