Table 2.

Comparison of different Approaches en Route to (−)-Crassinervicn Acid.^[a]

Product	Conditions	Conv. [%][b]	Yield [%][c]	e.r.[d]
22	A; 0.4 equiv. dbu, 22 °C, 14 h	>98	63	84:16
	B; 0.15 equiv. LiOtBu, 22 °C, 24 h	87	78	60:40
	C; 0.13 equiv. NaOtBu, −30 °C, 24 h	>98 (to 23)	82 (of 23)	69:31
23	A; 0.4 equiv. dbu, 35 °C, 8.0 h	>98	72	95:5
	B; 0.15 equiv. LiOtBu, 22 °C, 24 h	>98	19	nd
	C; 0.13 equiv. NaOtBu, −30 °C, 24 h	>98	<2	na
24	A; 1.4 equiv. dbu, 22 °C, 14 h	>98	70	88.5:11.5
	B; 1.15 equiv. LiOtBu, 22 °C, 24 h	>98	<10	nd
	C; 1.13 equiv. NaOtBu, −30 °C, 24 h	>98	22	nd

^[a]Conditions: i) HO(CH₂)₂OH, 10 mol % pTsOH•H₂O, tol., reflux, 12 h; 90% yield. ii) 3.0 equiv. tBuLi, thf, −78 °C; geranial, −78 °C, 2.0 h. iii) 1.0 mol % (n-Pr)₄NRuO₄, N-methylmorpholine N-oxide, CH₂Cl₂, 22 °C, 2.0 h. iv) 10 mol % pTsOH, acetone, 22 °C, 10 min.; 63% overall yield for three steps. v) NaClO₂, NaH₂PO₄•H₂O, tBuOH, H₂O, 2-methyl-2-butene, 22 °C, 3.0 h; 82% yield. Reactions were performed under N₂ atmosphere.

^[b]Determined by analysis of 400 MHz ¹H NMR spectra of unpurified mixtures (±2%).

^[c]Yields of isolated and purified products (±5%).

^[d]Determined by GC analysis (±2%). See the Supporting Information for details.