From Chiral Non-carbohydrates

The cis-isomeric alkenes gave all four possible isomers. The galantinic add derivative 56 was obtained from an L-serinal derivative in seven steps induding two chain-extension reactions.  

Reagents i. TbdmsCI, imidazole. DMF ii, KMn04, dicyclohexano-18-crown-6 iii, Me2C(OMe)2, H iv. Nal04 v. H3O vi. NaOMe vii. HOAc, H2O viii, NaBH4 ix, H3O  

NaNa vii, BU4NF viii, O3, MeOH, NaHCOa ix, NaBH4 x, AC2O, Py, DMAP xi. H2, Pd/C 

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From Chiral Non-carbohydrates - A section on amino-sugars has been included in a review of the synthesis of monosaccharides from non-carbohydrate sources. L-Ristosamine 42 was synthesized by addition of the Cs-synthon 40 (which contains a masked aldehyde function that can be readily demasked by mild acid hydrolysis) to the L-lactaldehyde derivative 41 (Scheme 11). The TBSOP adduct 43 (Vol.27, p.ll4), derived from 2,3-< -isopropylidene-D-glycer-aldehyde, has been converted into 3-amino-3-deoxy-D-altrose 46 by a route involving cis-hydroxylation of its unsaturated lactam moiety and periodate cleavage between C-6 and C-7 of the derived heptitol derivative 45 as key steps (Scheme 12). 3-Amino-3-deoxy-L-allose was obtained by converting 43 to its C-3... 

From Chiral Non-carbohydrates. - The 3-amino-3,6-dideoxy-hexose derivative 50 was the major product obtained from aldol condensation of the tricarbonyliron-diene complex 47 with the (R)-lactaldehyde derivative 48 (Scheme 14). Adduct 49 was the major (45%) of four isomers formed. If decom-plexation (step iv) preceded reduction (step ii), then the 2-epimer of 50 predominated. IV-Acetyl-L-daunosamine and its 5-C-isobutyl analogue (52) were synthesized from the corresponding cyanohydrin derivatives 51 by chain extension (Scheme 15). Aziridination of chiral traws-a,p-unsaturated esters such as 53 gave mainly two isomeric 2,3-epimines, e.g. 54 and 55 in the ratio 67 33 (Scheme... 

From chiral non-carbohydrates. - Several syntheses of amino-sugars from chiral non-carbohydrate starting materials have been reported. The a-L-daunosamine derivative 48 was obtained from L-aspartic acid via the known lactone 47, which was prepared in 2 steps. Key reactions were the anri-selective Grignard addition and syn-selective epoxidation (steps i and ii,... 

A number of synthesis of amino-sugars from chiral non-carbohydrate starting materials have been reported. A reaction sequence used previously to synthesize 2-amino-2-deoxy-D-ribose from 2,3-0-isopropylidene-D-glyceraldehyde (V0I.I6, p.92-3) has been improved K) achieve better stereoselectivity in the initial aldol condensation used to extend the chain by two carbon atoms. The synthesis of a 6,6,6-trifluoro-L-daunosamine derivative from 2,3-0-cyclohexylidene-D-glyceraldehyde is covered in Chapter 8, and of 2,5-dideoxy-2,5-imino-pentonic acids from tartaric acid in Chapter 16. 

Our work has mostly been focussed on the potential of selective transformation of aldonolactones, as will be described in this article, rather than on the synthesis of defined target molecules. Thus, the purpose of this paper is also to inspire researchers from the non-carbohydrate field to recognize these chiral synthons for further use in the synthesis of e.g.complex natural products. 

Chiral non-carbohydrate starting materials again feature in a number of amino-sugar syntheses. o-Allosamine (49) was prepared from the cycloadduct (48), the... 

Casu, F., Chiacchio, M.A., Romeo, R. and Gumina, G., Chiral synthesis of heterosubstituted nucleoside analogs from non-carbohydrate precursors. Curr. Org. Chem., 2007, 11, 1017-1032. 

From among the variety of non-carbohydrate precursors, acetylenes and alkenes have found wide application as substrates for the synthesis of monosaccharides. Although introduction of more than three chiral centers having the desired, relative stereochemistry into acyclic compounds containing multiple bonds is usually difficult, the availability of such compounds, as well as the choice of methods accessible for their functionalization, make them convenient starting-substances for the synthesis. In this Section is given an outline of all of the synthetic methods that have been utilized for the conversion of acetylenic and olefinic precursors into carbohydrates. Only reactions leading from dialkenes to hexitols are omitted, as they have already been described in this Series.7... 

Quite recently, Marco-Contelles [73] has made use of free radical cyclization and ring-closing metathesis in order to develop useful synthetic protocols to access a number of chiral non-racemic, densely oxygenated medium-sized carbocycles from carbohydrate precursors. 

Leukotrlenes and other Mediators - Comprehensive reviews on the chemistry, biosynthesis and metabolism, - and pharmacologyi of LTs have appeared (see also Chapter 24). Chiral starting materials have been employed in the enantiospecific synthesis of LTs C, and LTF, and LTF sulfone have been synthesized and their biological activities determined in the guinea pig (GP). Total syntheses of LTB, (non-carbohydrate based), LTB and 14,15-LTA, have been reportedIn the biosynthesis of LTs in human PMNs, it was shown that the 7-H (pro-S) hydrogen is removed from arachldonic acid (AA) to form 5-hydroperoxy-6E, 8Z, IIZ, 14Z-eicosatetraenoic acid (5-HPETE) and that the 10-D (pro-R)-hydrogen is eliminated in the conversion of 5-HPETE into LTA. 

In our laboratory we have developed a novel approach to the synthesis of an enantiopure AB segment of the anthracyclinones based on a new type of chiral substrate, enone 131 [131,132]. Di-O-acetyl-L-rhamnal (129), obtained from L-rhamnose, was converted into benzyl glycoside 130 [133] by the Perrier procediue [134], Hydrolysis and oxidation of the C-4 (carbohydrate numbering) hydroxyl group in 130 gave enone 131 in 67% overall yield (Scheme 27). It is worthy of note that uloside 131 is also readily available from a non-sugar chiral pool. Enzymatic resolution of racemic l-(2-furyl)ethanol yielded the (S)-enantiomer 138 in 98% ee [135]. This was transformed in two steps, by known procedures, into ulose 139 (Scheme 28) [136,137] from which uloside 131 was readily obtained. 

Reviews have appeared on the synthesis of inositols, carba sugars, conduritols and amino conduritols utilizing the non-carbohydrate sources of benzene cis-diols, quinic acid and Vogel s naked sugar methodology. Other reviews on the preparation of cyclophellitol and ep/-cyclophellitol from glycals and the use of D-glyceraldehyde as a chiral precursor in Diels-Alder and 1,3-dipolar cycloaddition approaches to carbocyclic derivatives have also been reported. 

Goldinonolactone (40) and the chiral tetrahydrofuran (41) were key intermediates in a chiral, but non-carbohydrate-based, synthesis of the antibiotic aurodox both these intermediates are also accessible from carbohydrates, (40) being made from an L—mannose derivative and (41) from D-mannose via a previously described acetyl-... 

Tietze has synthesized ethyl P-D-mannopyranoside from non-carbohydrate precursors [190]. The procedure involves [4-1-2] hetero Diels-Alder cycloaddition of the enol ether 122 and the chiral oxazolidinone 123 under promotion by Me2AlCl to give the dihydropyran 124 in very high diastereoselectivity. Reductive cleavage of... 

Roberts and co-workers have employed a number of chiral carbohydrate-derived thiols as polarity reversal catalysts in the radical hydrosilylation of electron-rich prochiral alkenes [68-70]. In these thiols, the SH group is attached to the anomeric carbon atom. Scheme 21 demonstrates the non-catalyzed reaction and in step b, the hydrogen atom transfer from the silane... 

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