1,3- diastereoselective reduction of β-hydroxyketones utilizing alkoxydialkylboranes

Enantio- and Diastereoselective Additions to Aldehydes Using the Bifunctional Reagent 2-(Chloromethyl)-3-(tributylstannyl)propene: Application to a Synthesis of the C16−C27 Segment of Bryostatin 1

“…Oxidative cleavage of the double bond and subsequent syn-reduction of the resulting hydroxy ketone under the conditions developed by Prasad 13 afforded the diol in high yields as a single isomer, thus providing key intermediate 23 with all stereocenters in place. The diol unit in 23 was then protected as its acetonide, from which the syn-diol relationship was confirmed by 13 C NMR. 14 Deprotection and oxidation of the primary hydroxyl group furnished the corresponding aldehyde, which was treated with an in situ generated prenyl indium reagent 15 to complete the carbon backbone of our target molecule.…”

Stereoselective Desymmetrization of 2,2‐Bishydroxymethyl‐1‐tetralones by Iodocyclization, Synthesis of Novel Enantiopure [6.6.5] Tricyclic Framework and Chemoenzymatic Diversity Generation

“…Several microbial/plant ketoreductases [16] were screened and we found that ketoreductase enzyme isolated from Geotrichum candidum (NBRC 5767) reduces the ketones in an antiPrelog fashion to afford the corresponding alcohols; whereas ketoreductases from Daucus carota, yeast, Candida parapsilosis (NBRC 1396) and Aspergillus niger (NBRC 4415) afford the corresponding alcohols in a Prelog fashion (Scheme 6). Chemical equivalents of the biocatalytic reduction have also been explored and we found that NaBH 4 yielded the same alcohols obtained from Prelog ketoreductases (PKR, A niger, C. parapsilosis, yeast and D. carota), whereas the Et 2 BOMe/NaBH 4 reagent system [17] yields the alcohols obtained from anti-Prelog ketoreductases (APKR, G. candidum). The stereochemistries of the final alcohols have been confirmed by X-ray crystal analysis (Scheme 7).…”

Totalsynthese von Thuggacin B

“…Die korrekte 1,4-Stereoinduktion wurde durch Analyse der Mosher-Ester von Hydroxyketon 21 bestätigt. Die Bildung des syn-Aldolprodukts wurde nach 1,3-syn-Diol-Bildung durch NaBH 4 in Gegenwart von Et 2 BOMe [23] gefolgt von Acetonidbildung bestätigt. Das Acetonid zeigte die erwarteten Kopplungskonstanten (J) und 13 C-chemischen Verschiebungen der Acetonid-Kohlenstoffatome.…”