Stereoselective acyclic ketone reduction

Synthesis of Polypropionate Fragments Containing Tertiary‐Alcohol Moieties. Cross‐aldolisations with lithium enolates of 7‐oxabicyclo[2.2.1]heptan‐2‐one derivatives

“…71 (80) 2980, 2920, 2880, 1725, 1380, 1250, 1200, 1165, 1100, 1010, 925, 870, 850, 830. 3.54(dd,2J = 11.5,,J = 0.8, H'-C (7));2.21 (s, Me (1)); 1.75(dddq,'J = 2.6,2.3,0.8,6.9,H-C (6) (5)); 68.6 (I, 'J(C,H) = 143, C(7)); 29.9 (d, 'J(C,H) = 128, C(6)); 29.7,28.8,28.1,26.4,21.2, 18.2, 13.9 (7q, 'J(C,H) = 125-129, 7 Me). CI-MS (NH,): 271 (II), l85 (8), 157 (13), 129(100), 127(10), 115 (17), 114 (13), 111 (25),99(48),97 (18),87 (27),85(15),71 (48).…”

Structural elucidation of naturally occurring 9, 12, 13-trihydroxy fatty acids by a synthetic study.

“…The primary basis for assigning the relative stereochemistry at the 12 and 13 positions of trihydroxy acids is the known specificity of the coupling constant of the corresponding aceto-nide derivatives. When the acyclic vicinal diol is fixed by the acetonide ring, the coupling constant between the vicinal protons of the acetonide ring has been reported to be 7-8 Hz and 4-6Hz in the cases of threo and erythro diols, respectively.6) Since the natural materials were isolated in minute quantities and seemed at room temperature delivered the threo diol (6) in an 87% yield from 3 (Scheme 1).9) Acetonide formation in 6 was followed by oxidation with m-chloroperoxybenzoic acid to afford a 2 : 1 mixture of epoxy acetonides (7). Although the relative configuration of the resulting epoxide ring was not precisely assigned at this stage, the later experiments revealed that the major isomer had an anti-relationship between the epoxide ring and the C-12 oxygen.…”

Structural Elucidation of Naturally Occurring 9,12,13-Trihydroxy Fatty Acids by a Synthetic Study1)

“…The ethereal solution was evaporated, and the resulting residue (1.2 g) was passed through a Si02 (60 g) column, eluting with hexane-AcOEt (20: I) to obtain the first recovered ester (191 mg, 17%), next 12,13-epoxylinoleate (3, 272mg, 22%), then a I: 5 mixture of 3 and 9,10-epoxylinoleate (500mg), and finally a mixture of diepoxides (67 mg, 2. (6). A mixture of methyl 12,13-epoxylinoleate (3, 1.65 g) and NaOAc (3.43 g) in AcOH (25 ml) was stirred at 80 D C for 2hr.…”

“…Trans opening of the epoxide ring under the conditions employed is well precedented in related systems. 8 ) Treatment of the resultant mixture with lithium hydroxide at room temperature delivered the threo diol (6) in an 87% yield from 3 (Scheme 1).9) Acetonide formation in 6 was followed by oxidation with m-chloroperoxybenzoic acid to afford a 2: 1 mixture of epoxy acetonides (7). Although the relative configuration of the resulting epoxide ring was not precisely assigned at this stage, the later experiments revealed that the major isomer had an anti-relationship between the epoxide ring and the C-12 oxygen.…”