“…From here, a parallel cross-metathesis with 3a (containing the 42,45- anti configuration) mediated by Hoveyda–Grubbs II catalyst (13 mol%), followed by PMB ether cleavage, gave the separate C29–C46 fragments 32,36- anti 21 and 32,36- syn 22 . 23 Global desilylation under fluorous conditions then gave the truncated tetraols 2a and 2b for detailed NMR spectroscopic comparison. An analogous sequence with 3b (42,45- syn configuration) and ent - 4a provided the 32,36- syn , 42,45- syn diastereomer 2c .…”