Subscribe to RSS
Please copy the URL and add it into your RSS Feed Reader.
https://www.thieme-connect.de/rss/thieme/en/10.1055-s-00000083.xml
Synlett 2015; 26(02): 250-258
DOI: 10.1055/s-0034-1379603
DOI: 10.1055/s-0034-1379603
letter
Total Synthesis of Quercitols: (+)-allo-, (–)-proto-, (+)-talo-, (–)-gala-, (+)-gala-, neo-, and (–)-epi-Quercitol
Further Information
Publication History
Received: 25 September 2014
Accepted after revision: 29 October 2014
Publication Date:
17 December 2014 (online)
![](https://www.thieme-connect.de/media/synlett/201502/lookinside/thumbnails/10.1055-s-0034-1379603-1.jpg)
Abstract
The cyclohexenenones exo- and endo-2 were converted into the cyclohexenyl acetates exo- and endo-3 and exo- and endo-5 with a diastereoselectivity of >99:1 (2 steps). Ether cleavage with DDQ in CH2Cl2/H2O (20:1) and in situ ketal hydrolysis afforded the cyclohexenones 6 and 7 in up to 83% and 87% yield, respectively. Compound 6 was converted into (+)-allo- and (–)-proto-quercitol with a diastereoselectivity of 100:0 (4 steps). Moreover, 6 was carried on to (–)-talo-quercitol whereas 7 furnished the four remaining title quercitols (3–5 steps) including both enantiomers of gala-quercitol.
Key words
cyclohexenones - diastereoselectivity - ether cleavage - α-hydroxy ketone - oxidation - reductionSupporting Information
- Supporting information for this article is available online at http://dx.doi.org/10.1055/s-0034-1379603.
- Supporting Information
-
References and Notes
- 1 Aucktor J, Anselmi C, Brückner R, Keller M. Synlett 2014; 25: 1312
- 2a Reviews: Hudlicky T, Cebulak M. Cyclitols and their Derivatives: A Handbook of Physical, Spectral, and Synthetic Data. Verlag Chemie; Weinheim: 1993
- 2b Gueltekin MS, Celik M, Balci M. Curr. Org. Chem. 2004; 8: 1159
- 3 Synthesis of (+)-allo-quercitol (8a): Yadav JS, Maiti A, Sankar AR, Kunwar AC. J. Org. Chem. 2001; 66: 8370
- 4 C-3 of this compound represents a chirotopic nonstereogenic center. Because of the latter attribute it suffices to connect C-3 and 3-OH by an ‘ordinary bond’ rather than by a wedge or by hatches.
- 5a McCasland GE, Naumann MO, Durham LJ. J. Org. Chem. 1968; 33: 4220
- 5b Angyal SJ, Odier L. Carbohydr. Res. 1982; 101: 209
- 5c Gültekin MS, Çelik M, Turkut E, Tanyeli C, Balci M. Tetrahedron: Asymmetry 2004; 15: 453 ; corrigendum: Tetrahedron: Asymmetry 2004, 15, 1959
- 6a McCasland GE, Furuta S, Johnson LF, Shoolery JN. J. Am. Chem. Soc. 1961; 83: 2335
- 6b Angelaud R, Babot O, Charvat T, Landais Y. J. Org. Chem. 1999; 64: 9613
- 6c Hydloft L, Madsen R. J. Am. Chem. Soc. 2000; 122: 8444
- 6d Ref. 3.
- 7a Ref. 6a.
- 7b Dubreuil D, Cleophax J, Vieira de Almeida M, Verre-Sebrié C, Liaigre J, Vass G, Gero SD. Tetrahedron 1997; 53: 16747
- 7c Ref. 6b.
- 7d Maezaki N, Nagahashi N, Yoshigami R, Iwata C, Tanaka T. Tetrahedron Lett. 1999; 40: 3781
- 7e Ref. 6c.
- 7f Shih T.-L, Lin Y.-L. Synth. Commun. 2005; 35: 1809
- 7g Murugan A, Yadav AK, Gurjar MK. Tetrahedron Lett. 2005; 46: 6235
- 8a Ref. 5b.
- 8b Shih T.-L, Lin Y.-L, Kuo W.-S. Tetrahedron 2005; 61: 1919
- 9a Ref. 5b.
- 9b Kühlmeyer R, Keller R, Schwesinger R, Netscher T, Fritz H, Prinzbach H. Chem. Ber. 1984; 117: 1765
- 9c Ref. 8b.
- 9d Murali C, Gurale BP, Shashindhar MS. Eur. J. Org. Chem. 2010; 755
- 9e Aydin G, Savran T, Aktaş F, Baran A, Balci M. Org. Biomol. Chem. 2013; 11: 1511
- 10a Ref. 7b.
- 10b Biamonte MA, Vasella A. Helv. Chim. Acta 1998; 81: 688
- 10c Horne G, Potter BV. L. Chem. Eur. J. 2001; 7: 80
- 10d Ref. 7f; therein 8f was referred to as dextrorotatory. In accordance therewith, synthetic ent-8f was referred to as levorotatory in ref. 8b. The two findings disagree with our synthetic 8f being levorotatory (Scheme 7).
- 11 DDQ oxidations of primary PMB ethers of primary or secondary alcohols giving p-methoxybenzaldehyde plus these alcohols: Oikawa Y, Yoshioka T, Yonemitsu O. Tetrahedron Lett. 1982; 23: 885
- 12 DDQ oxidations of secondary PMB ethers (specifically: p-methoxybenzhydryl ethers) of primary alcohols giving p-methoxybenzophenone plus these alcohols: Sharma GV. M, Prasad TR, Rakesh SB. Synth. Commun. 2004; 34: 941
- 13 DDQ oxidations of secondary PMB esters of carboxylic acids giving p-methoxyacetophenone plus these carboxylic acids: Yoo S.-E, Kim HR, Yi KY. Tetrahedron Lett. 1990; 31: 5913
- 14 The benzylic C–O bond in the 1,4-dioxane moieties of the tricyclic cyclohexanetriol triacetates1 41 was cleaved with DDQ in CH2Cl2/H2O (20:1), and the resulting alcohols were benzoylated. This provided the nonhydrolyzable spiroketals 9a–e in overall yields around 90% (Scheme 8).
- 15a In the tricyclic cyclohexanetriol triacetate 41b (which now rendered the spiroketal 9b by oxidative cleavage as depicted in Scheme 8) we had been able to cleave1 the benzylic C–O bond by an ionic hydrogenolysis with Et3SiH/F3CCO2H.15b We then effected a benzylic bromination, whereupon treatment with Zn induced a reductive elimination; it ring-opened the spiroketal moiety.1 The scope and limitations of that approach have not yet been investigated.
- 15b Ma Z, Hu H, Xiong W, Zhai H. Tetrahedron 2007; 63: 7523
- 16 pK a1 of DDQ-H2 (16): Akutagawa T, Saito G. Bull. Chem. Soc. Jpn. 1995; 68: 1753
- 17 Ammonolysis of pentaacetate rac-25: see ref. 22c.
- 18 In the present work we terminated the synthesis of each quercitol by an ammonolysis, the substrate of which was a pentaacetate (Scheme 4: 25 → 8g, 26 → 8a; Scheme 7: 37 → 8f), a triacetate (Scheme 5: 29 → 8c; Scheme 6: 35 → 8d; Scheme 7: 39 → 8e) or a mixed oligocarboxylate (Scheme 6; post-34 → ent-8d). Each ammonolysis was executed under conditions described by Balci et al.22c for two analogous ammonolyses.
- 19 NMR Data of (–)-proto-Quercitol (8b, Figure 1) 1H NMR (500 MHz, D2O): δ = 1.80 (ddd, J gem = 14.0 Hz, J 6-Hax,1 = 11.7 Hz, J 6-Hax,5 = 3.1 Hz, 1 H, 6-Hax), 1.98 (dddd, J gem = 14.0 Hz, J 6-Heq,1 = 4.8 Hz, J 6-Heq,5 = 3.3 Hz, 4 J 6-Heq,4 = 1.2 Hz, 1 H, 6-Heq), 3.55 (dd, J 2,3 = 9.7 Hz, J 2,1 = 9.1 Hz, 1 H, 2-H), 3.70 (dd, J 3,2 = 9.7 Hz, J 3,4 = 3.3 Hz, 1 H, 3-H), 3.74 (ddd, J 1,6-Hax = 11.7 Hz, J 1,2 = 9.1 Hz, J 1,6-Heq = 4.8 Hz, 1 H, 1-H), 3.92 (ddd, J 4,5 = 3.6 Hz, J 4,3 = 3.3 Hz, 4 J 4,6-Heq = 1.2 Hz, 1 H, 4-H), 4.01 (ddd, J 5,4 = 3.6 Hz, J 5,6-Heq = 3.3 Hz, J 5,6-Hax = 3.1 Hz, 1 H, 5-H) ppm.
- 20 Preparation of cyclohexenetriol triacetate 20 from cyclohexa-1,4-diene by an oxidation to endo-peroxide/hydroperoxide and an enzymatic kinetic resolution: see ref. 5c.
- 21 Preparation of cyclohexenetriol triacetate ent-20 from d-(–)-quinic acid: Shih T.-L, Kuo W.-S, Lin Y.-L. Tetrahedron Lett. 2004; 45: 5751
- 22a Seçen H, Salamci E, Sütbeyaz Y, Balci M. Synlett 1993; 609
- 22b Gültekin MS, Salamci E, Balci M. Carbohydr. Res. 2003; 338: 1615
- 22c Salamci E, Seçen H, Sütbeyaz Y, Balci M. J. Org. Chem. 1997; 62: 2453
- 22d Salamci E, Seçen H, Sütbeyaz Y, Balci M. Synth. Commun. 1997; 27: 2223
- 23 Method: Dupau P, Epple R, Thomas AA, Fokin VV, Sharpless KB. Adv. Synth. Catal. 2002; 344: 421
- 24 Dihydroxylation of cyclohexenetriol triacetate 20 with OsO4/ N-methylmorpholine-N-oxide: see ref. 5c.
- 25 Dihydroxylations of cyclohexenetriol triacetates ent-20 and rac-20 with KMnO4: see ref. 21, 22a,c.
- 26a Evans DA, Chapman KT. Tetrahedron Lett. 1986; 27: 5939
- 26b Evans DA, Chapman KT, Carreira EM. J. Am. Chem. Soc. 1988; 110: 3560
- 26c Bao X, Cao Y.-X, Chu W.-D, Qu H, Du J.-Y, Zhao X.-H, Ma X.-Y, Wang C.-T, Fan C.-A. Angew. Chem. Int. Ed. 2013; 52: 14167
- 26d Griffith DR, Botta L, St Denis TG, Snyder SA. J. Org. Chem. 2014; 79: 88
- 26e Shangguan N, Kiren S, Williams LJ. Org. Lett. 2007; 9: 1093
- 27 Example for stereocomplementary diastereoselective α-hydroxycyclohexanone reductions with LiBH(s-Bu)3 vs. triacyloxyborohydride: Breit B, Bigot A. Chem. Commun. 2008; 6498
- 28 The ammonolysis of the pentaacetate ent-26 was described in ref. 8b.
- 29 NMR Data of (+)-allo-Quercitol (8a, Figure 2) 1H NMR (500 MHz, D2O; 323 K): δ = 1.59 (ddd, J gem = 14.1 Hz, J 6-Hax,5 = 9.4 Hz, J 6-Hax,1 = 3.3 Hz, 1 H, 6-Hax), 2.12 (ddd, J gem = 14.1 Hz, J 6-Heq,1 = 6.1 Hz, J 6-Heq,5 = 4.4 Hz, 1 H, 6-Heq), 3.56 (dd, J 4,5 = 8.0 Hz, J 4,3 = 3.1 Hz, 1 H, 4-H), 3.79 (dd, J 2,3 = 3.1 Hz, J 2,1 = 3.1 Hz, 1 H, 2-H), 4.01 (ddd, J 3,2 = 3.1 Hz, J 3,4 = 3.1 Hz, 4 J 3,1 = 1.3 Hz, 1 H, 3-H), 4.03 (ddd, J 5,6-Hax = 9.4 Hz, J 5,4 = 8.0 Hz, J 5,6-Heq = 4.4 Hz, 1 H, 5-H), 4.05 (dddd, J 1,6-Heq = 6.1 Hz, J 1,6-Hax = 3.3 Hz, J 1,2 = 3.1 Hz, 4 J 1,3 = 1.3 Hz, 1 H, 1-H) ppm.
- 30 Method: Fujii H, Oshima K, Utimoto K. Chem. Lett. 1991; 1847
- 31 Still WC, Kahn M, Mitra A. J. Org. Chem. 1978; 43: 2923
- 32 Synthesis of cyclohexenetriol triacetate 30 by an asymmetric eliminative epoxide opening: de Sousa SE, O’Brien P, Pilgram CD. Tetrahedron 2002; 58: 4643
- 33 Dihydroxylations of cyclohexenetriol triacetate ent-30 with KMnO4 or RuO4 gave an almost 1:1 ratio of the corresponding glycols ent-28 and ent-29; after peracetylation, the combined overall yield was 74%, see ref. 8b.
- 34 NMR Data of (+)-talo-Quercitol (8c, Figure 3) 1H NMR (500 MHz, D2O, 313 K): δ = 1.82–1.92 (m, 2 H, 6-H2), 3.71 (dd, J 4,3 = 9.9 Hz, J 4,5 = 3.1 Hz, 1 H, 4-H), 3.75 (dd, J 3,4 = 9.9 Hz, J 3,2 = 2.7 Hz, 1 H, 3-H), 3.99 (ddd, J 1,6-Hax = 10.6 Hz, J 1,6-Heq = 5.9 Hz, J 1,2 = 2.8 Hz, 1 H, 1-H), 4.03 (ddd, J 2,1 = 2.8 Hz, J 2,3 = 2.7 Hz, 4 J 2,6-Heq = 1.2 Hz, 1 H, 2-H), 4.07 (ddd, J 5,6-Heq = 3.3 Hz, J 5,6-Hax = 3.3 Hz, J 5,4 = 3.3 Hz, 1 H, 5-H) ppm.
- 35 For a different synthesis of cyclohexenetriol triacetate 32: see ref. 32.
- 36 Synthesis of cyclohexenetriol triacetate ent-32 from d-(–)-quinic acid: see ref. 8b.
- 37 Synthesis of cyclohexenetriol triacetate rac-32 from cyclohexa-1,4-diene: see ref. 22c.
- 38 Dihydroxylation of cyclohexenetriol triacetate rac-32 with OsO4/NMO: see ref. 22c.
- 39 Dihydroxylations of cyclohexenetriol triacetate ent-32 with KMnO4 or RuO4: see ref. 8b.
- 40 NMR Data of (–)-gala-Quercitol (8d, Figure 4) 1H NMR (500 MHz, D2O): δ = 1.72 (ddd, J gem = 12.3 Hz, J 6-Hax,5 = 11.4 Hz, J 6-Hax,1 = 10.6 Hz, 1 H, 6-Hax), 2.00 (dddd, J gem = 12.3 Hz, J 6-Heq,1 = 4.6 Hz, J 6-Heq,5 = 4.4 Hz, 4 J 6-Heq,4 = 1.3 Hz, 1 H, 6-Heq), 3.67 (dd, J 2,1 = 9.1 Hz, J 2,3 = 3.2 Hz, 1 H, 2-H), 3.79 (ddd, J 1,6-Hax = 10.6 Hz, J 1,2 = 9.1 Hz, J 1,6-Heq = 4.6 Hz, 1 H, 1-H), 3.92 (ddd, J 4,3 = 4.3 Hz, J 4,5 = 3.1 Hz, 4 J 4,6-Heq = 1.3 Hz, 1 H, 4-H), 4.00 (dd, J 3,4 = 4.3 Hz, J 3,2 = 3.2 Hz, 1 H, 3-H), 4.01 (ddd, J 5,6-Hax = 11.4 Hz, J 5,6-Heq = 4.4 Hz, J 5,4 = 3.1 Hz, 1 H, 5-H) ppm.
- 41a Adkins H, Roebuck AK. J. Am. Chem. Soc. 1948; 70: 4041
- 41b Ogawa S, Aoki Y, Takagaki T. Carbohydr. Res. 1987; 164: 499
- 41c Doddi VR, Kumar A, Vankar YD. Tetrahedron 2008; 54: 9117
- 42 In principle, the epoxidation of cyclohexenol 34 may lead to the syn- and/or the anti-epoxide (Scheme 9). If the Fürst–Plattner rule is respected, the ring opening of either epoxide should deliver the respective ‘diaxially substituted dihydroxyformate’ initially, that is, compounds 43 and iso-43, respectively. In the sequel, each of these dihydroxyformates would furnish (+)-gala-quercitol (ent-8d).
- 43 NMR Data of (+)-gala-Quercitol (ent-8d, Figure 5) 1H NMR (500 MHz, CD3OD): δ = 1.77 (ddd, J gem = 12.3 Hz, J 6-Hax,1 = 10.4 Hz, J 6-Hax,5 = 10.4 Hz, 1 H, 6-Hax), 1.90 (dddd, J gem = 12.3 Hz, J 6-Heq,1 = 4.4 Hz, J 6-Heq,5 = 4.4 Hz, 4 J 6-Heq,2 = 1.2 Hz, 1 H, 6-Heq), 3.64 (dd, J 4,5 = 8.5 Hz, J 4,3 = 3.2 Hz, 1 H, 4-H), 3.73 (ddd, J 5,6-Hax = 10.0 Hz, J 5,4 = 8.6 Hz, J 5,6-Heq = 4.4 Hz, 1 H, 5-H), 3.81 (dd, J 2,3 = 5.0 Hz, J 2,1 = 2.9 Hz, 1 H, 2-H), 3.91 (dd, J 3,2 = 5.0 Hz, J 3,4 = 3.3 Hz, 1 H, 3-H), 3.95 (ddd, J 1,6-Hax = 10.6 Hz, J 1,6-Heq = 4.4 Hz, J 1,2 = 2.9 Hz, 1 H, 1-H) ppm.
- 44 Dihydroxylations of cyclohexenetriol triacetate ent-38 with KMnO4 or RuO4 provided the glycols ent-39 and ent-40 with dr = 58:42 in 65% and 77% combined yield, respectively; see ref. 8b.
-
45a Sharpless KB, Amberg W, Bennani YL, Crispino GA, Hartung J, Jeong K.-S, Kwong H.-L, Morikawa K, Wang Z.-M, Xu D, Zhang X.-L. J. Org. Chem. 1992; 57: 2768 ; (in the presence of MeSO2NH2)
- 45b See footnote 6 in: Jeong K.-S, Sjö P, Sharpless KB. Tetrahedron Lett. 1992; 33: 3833 ; (in the absence of MeSO2NH2)
- 45c Zaitsev AB, Adolfsson H. Synthesis 2006; 1725
- 45d Noe MC, Letavic MA, Snow SL, McCombie S. Org. React. 2005; 66: 109
- 45e Kolb HC, Sharpless KB In Transition Metals for Organic Synthesis . Vol. 2. Beller M, Bolm C. Wiley-VCH; Weinheim: 2004: 275-298
- 46 The relative amounts of the quercitol pentaacetates 36 and 37 were determined from the integrals over non-overlapping 1H NMR signals (400 MHz, CDCl3) of this mixture. Their resonances are printed in boldface in the following enumerations:NMR Data of Pentaacetate 36 1H NMR (400 MHz, CDCl3): δ = 1.53 (dt, J gem = 12.5 Hz, J 6-Hax,1 = J 6-Hax,5 = 11.7 Hz, 1 H, 6-Hax), 1.99 (s, 6 H, 2 × O2CCH3), 2.02 (s, 6 H, 2 × O2CCH3), 2.15 (s, 3 H, 3-O2CCH3), 2.52 (dt, J gem = 12.5 Hz, J 6-Heq,1 = J 6-Heq,5 = 5.1 Hz, 1 H, 6-Heq), 5.03 (dd, J 2,1 = 10.2 Hz, J 2,3 = 2.9 Hz, 2 H, 2-H and 4-H), 5.24 (ddd, J 1,6-Hax = 11.7 Hz, J 1,2 = 10.2 Hz, J 1,6-Heq = 5.1 Hz, 2 H, 1-H and 5-H), 5.59 (t, J 3,2 = J 3,4 = 2.9 Hz, 1 H, 3-H) ppm.NMR Data of Pentaacetate 37 (Figure 6) 1H NMR (400 MHz, CDCl3): δ = 1.99 (s, 3 H, O2CCH3), 2.00 (s, 3 H, O2CCH3), 2.01 (s, 3 H, O2CCH3), 2.03 (s, 3 H, O2CCH3), 2.04 (ddd, J 6-Hax,1 = 12.5 Hz, J gem = 12.1 Hz, J 6-Hax,5 = 11.9 Hz, 1 H, 6-Hax), 2.17 (s, 3 H, O2CCH3), 2.22 (dddd, J gem = 12.1 Hz, J 6-Heq,5 = 5.2 Hz, J 6-Heq,1 = 4.7 Hz, 4 J 6-Heq,2 = 1.3 Hz, 1 H, 6-Hax), 4.95 (ddd, J 5,6-Hax = 11.9 Hz, J 5,4 = 9.7 Hz, J 5,6-Heq = 5.2 Hz, 1 H, 5-H), 4.97 (dd, J 3,4 = 10.5 Hz, J 3,2 = 2.8 Hz, 1 H, 3-H), 4.98 (ddd, J 1,6-Hax = 12.5 Hz, J 1,6-Heq = 4.7 Hz, J 1,2 = 2.6 Hz, 1 H, 1-H), 5.40 (dd, J 4,3 = 10.5 Hz, J 4,5 = 9.7 Hz, 1 H, 4-H), 5.55 (ddd, J 2,3 = 2.8 Hz, J 2,1 = 2.6 Hz, 4 J 2,6-Heq, = 1.3 Hz, 1 H, 2-H) ppm.
- 47 The authors of ref. 8b peracetylated the mixture of glycols ent-39 and ent-40 (mentioned in ref. 44) to obtain the pentaacetates (meso)-36 and ent-37. They separated the latter compounds by flash chromatography on silica gel, which we could not.
- 48a Chida N, Ohtsuka M, Nakazawa K, Ogawa S. J. Org. Chem. 1991; 56: 2976
- 48b Mahapatra T, Nanda S. Tetrahedron: Asymmetry 2010; 21: 2199
- 49 According to ref. 8b, an ammonolysis of the pentaacetate (meso)-36 (mentioned in ref. 47) rendered the quercitol 8e. Likewise, an ammonolysis of the pentaacetate ent-37 (also mentioned in ref. 47) gave the quercitol ent-8f. Both quercitols were diastereomerically pure.
- 50 NMR Data of neo-Quercitol (8e, Figure 7) 1H NMR (500 MHz, D2O): δ = 1.32 (dt, J gem = 12.3 Hz, J 6-Hax,1 = J 6-Hax,5 = 11.8 Hz, 1 H, 6-Hax), 2.18 (dt, J gem = 12.3 Hz, J 6-Heq,1 = J 6-Heq,5 = 4.8 Hz, 1 H, 6-Heq), 3.44 (dd, J 2,1 = 9.7 Hz, J 2,3 = 3.0 Hz, 2 H, 2-H and 4-H), 3.79 (ddd, J 1,6-Hax = 11.8 Hz, J 1,2 = 9.7 Hz, J 1,6-Heq = 4.8 Hz, 2 H, 1-H and 5-H), 4.03 (t, J 3,2 = J 3,4 = 3.0 Hz, 1 H, 3-H) ppm.
- 51 NMR Data of (–)-epi-Quercitol (8f, Figure 8) 1H NMR (400 MHz, D2O): δ = 1.74 (mc, 1H, 6-Hax), 1.96 (mc, 1 H, 6-Heq), 3.67 - 3.54 (m, 3 H, 3-H, 4-H, 5-H), 3.77 (ddd, J 1,6-Hax = 12.3 Hz, J 1,6-Heq = 4.5 Hz, J 1,2 = 2.7 Hz, 1 H, 1-H), 3.98 (mc, 1 H, 2-H) ppm.
- 52 We reached five quercitols of the present study via a total of four diastereoisomeric cyclohexenetriol triacetate precursors: 20 [Scheme 4; → (–)-proto-quercitol (8b)], 30 [Scheme 5; → (+)-talo-quercitol (8c)], 32 [Scheme 6; → (–)-gala-quercitol (8d)], and 38 [Scheme 7; → neo-quercitol (8e) and (–)-epi-quercitol (8f)]. The value of the eight stereoisomeric cyclohexenetriol triacetates as precursors of synthetic cyclohexitols was recognized previously by Balci et al.22 and by: Kee A, O’Brien P, Pilgram CD, Watson ST. Chem. Commun. 2000; 1521
Syntheses of (–)-proto-quercitol (8b):
Syntheses of (+)-talo-quercitol (8c):
Syntheses of (–)-gala-quercitol (8d):
Syntheses of (+)-gala-quercitol (ent-8d):
Syntheses of neo-quercitol (8e):
Syntheses of (–)-epi-quercitol (8f):
Syntheses of cyclohexenetriol triacetate rac-20 from cyclohexa-1,4-diene:
OH-Directed triacetoxyborohydride reductions of β-hydroxyketones were studied in depth by
OH-Directed diastereoselective triacetoxyborohydride reduction of an α-hydroxycyclohexenone:
OH-Directed diastereoselective triacetoxyborohydride reduction of an α-hydroxybi-cyclo[2.2.2]octanone:
OH-Directed diastereoselective triacetoxyborohydride reduction of a 4-hydroxydihydro-2H-pyran-3(4H)-one:
Method:
First descriptions of the AD-mix protocols:
Recent reviews:
Complementary diastereocontrol of cyclohexene dihydroxylations due to the presence of DHQ- vs. DHQD-substituted ligands: