Amino acids osmium tetroxide

Amino-Hydroxylation. A related reaction to asymmetric dihydroxylation is the asymmetric amino-hydroxylation of olefins, forming v/c-ami noalcohols. The vic-hydroxyamino group is found in many biologically important molecules, such as the (3-amino acid 3.10 (the side-chain of taxol). In the mid-1970s, Sharpless76 reported that the trihydrate of N-chloro-p-toluenesulfonamide sodium salt (chloramine-T) reacts with olefins in the presence of a catalytic amount of osmium tetroxide to produce vicinal hydroxyl p-toluenesulfonamides (Eq. 3.16). Aminohydroxylation was also promoted by palladium.77... 

Gallc er and co-workers devised a formal enantioselective synthesis of ( — )-3 in wduch the stereogenic center at C-6 was derived fiom Cbz-protected (S)-2-amino-4-pentenoic acid (36) (44). Acylation of 3,3-dimethoxy-pyrrolidine (37) with this acid yielded amide 38, which was converted into aldehyde 39 by cleavage of the terminal alkene vnth osmium tetroxide and sodium periodate (Scheme 5). The indolizidine nucleus was constructed from 39 by a problematic intramolecular aldol condensation, which was eventually optimized by using 2,2,6,6-tetramethylpiperidine as base followed by adsorption onto, and elution from, silica gel (45). Diastereoselective reduction of the ketone group of the aldol product 40 was accomplished in better than 95% enantiomeric excess (ee) with the Corey... 

Alder route, was converted into the urethan (25) by a series of unexceptional steps. Arndt-Eistert homologation of (25) provided the carboxylic acid (26) which, upon treatment with acetic anhydride, readily gave the lactam (27). Introduction of a one-carbon unit into the aromatic ring was achieved with chloromethyl methyl ether, and further reductive and hydrolytic modification afforded the amino-alcohol (28). Osmium tetroxide oxidation of (28) yielded the stereoisomeric triols (29) (20%) and (30) (22%) which were separated and oxidized to ( + )-clivonine (31) and (+ )-clividine (32), respectively. 

The lactone derivatives (369) prepared from L-glutamic acid (2-amino-2,3,4-trideoxy-L- /ycero-pentaric acid) can be converted into the 5,5-di-C-methylpent-ose derivative (370) by the reactions outlined in Scheme 65. A salient feature of the synthesis is that the chirality of L-glutamic acid is preserved at C-2 of (370). The enone (371) [prepared from 2-(2-furyl)propan-2-ol] has been converted into methyl 2,3-0-isopropylidene-5,5-di-C-methyl-P-DL-ribopyranoside (372) by cis-dihydroxylation (silver chlorate-osmium tetroxide) and stereoselective reduction (lithium aluminium hydride) of the 2,3-0-isopropylidene derivative of the resulting diol. ... 

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