2.1.8. Michael Reaction 2245 2.1.9. Others 2247 2.2. Cyclization Reactions 2248 2.2.1. Carbon Diels−Alder Reactions 2248 2.2.2. Aza-Diels−Alder Reactions 2252 2.2.3. Other Hetero-Diels−Alder Reactions 2255 2.2.4. Ionic Diels−Alder Reaction 2256 2.2.5. 1,3-Dipolar Cycloadditions 2256 2.2.6. Other Cycloaddition Reactions 2258 2.2.7. Prins-type Cyclization 2259 2.3. Friedel−Crafts Acylation and Alkylation 2259 2.4. Baylis−Hillman Reaction 2263 2.5. Radical Addition 2264 2.6. Heterocycle Synthesis 2267 2.7. Diazocarbonyl Insertion 2270 3. C−X (X ) N, O, P, Etc.) Bond Formation 2271 3.1. Aromatic Nitration and Sulfonylation 2271 3.2. Michael Reaction 2272 3.3. Glycosylation 2273 3.4. Aziridination 2275 3.5. Diazocarbonyl Insertion 2276 3.6. Ring-Opening Reactions 2277 3.7. Other C−X Bond Formations 2280 4. Oxidation and Reduction 2280 4.1. Oxidation 2280 4.2. Reduction 2281 5. Rearrangement 2283 6. Protection and Deprotection 2285 6.1. Protection 2285 6.2. Deprotection 2288 7. Polymerization 2291 8. Miscellaneous Reactions 2291 9. Lanthanide(II) Triflates in Organic Synthesis 2295 10. Conclusion 2295 11. Acknowledgment 2295 12. References 2295

Rare-earth metal triflates in organic synthesis

In view of the impending transition of chemical industry from depleting fossil raw materials to renewable feedstocks — the end of cheap oil is predicted around 2040 — this account gives an overview on chemically and enzymatically transforming carbohydrates, by far the major part of the annually regrowing biomass, into products with versatile industrial application profiles and the potential to eventually replace those presently derived from petrochemical sources.



The article contains sections titled: 

1.	Introduction	
2.	Availability of Carbohydrates	
3.	Current Nonfood Industrial Products from Sugars	
3.1.	Ethanol	
3.2.	Furfural	
3.3	d-Sorbitol	
3.4	Lactic Acid and Polylactic Acid (PLA)	
3.5.	Sugar-Based Surfactants	
3.5.1.	‘Sorbitan’ Esters	
3.5.2.	N-Methyl-N-acyl-glucamides (NMCA)	
3.5.3.	Alkylpolyglucosides (APG)	
3.5.4.	Sucrose Fatty Acid Monoesters	
3.6.	Pharmaceuticals and Vitamins	
4.	Toward Further Sugar-based Chemicals: Potential Development Lines	
4.1.	Furan Compounds	
4.1.1.	5-Hydroxymethylfurfural (HMF)	
4.1.2.	2,5-Dimethylfuran (DMF)	
4.1.3.	Furans with a Tetrahydroxybutyl Side Chain	
4.2.	Dihydropyrones	
4.3.	Sugar-Derived Unsaturated Nitrogen Heterocycles	
4.3.1.	Pyrroles	
4.3.2.	Pyrazoles	
4.3.3.	Imidazoles	
4.3.4.	3-Pyridinols	
4.4.	Toward Sugar-Based Aromatic Chemicals	
4.5.	Microbial Conversion of Six-Carbon-Sugars into Simple Carboxylic Acids and Alcohols	
4.5.1.	Carboxylic Acids	
4.5.2.	Potential Sugar-Based Alcohol Commodities by Microbial Conversions	
4.6.	Chemical Conversion of Sugars into Carboxylic Acids	
4.7.	Biopolymers from Polymerizable Sugar Derivatives	
4.7.1.	Synthetic Biopolyesters	
4.7.2.	Microbial Polyesters	
4.7.3.	Polyamides	
5.	Outlook	
6.	References

/pdf/carbohydrates-as-organic-raw-materials-49ddlx9da2.pdf

Carbohydrates as Organic Raw Materials

Reserpine: A Challenge for Total Synthesis of Natural Products

Synthesis of seven-membered oxacycles

Glycals (or usually their O-substituted derivatives) are readily converted into 2,3-unsaturated glycosyl compounds with O-, C-, N-, S- or otherwise linked substituents at the anomeric position. These products have been found to be useful for a range of synthetic purposes. In particular, the C-glycosidic compounds have served as readily available starting materials for the preparation of useful non-carbohydrate compounds. While these allylic rearrangement processes are usually conducted under the influence of Lewis acid catalysts, adaptations that involve activation of the allylic substituents of the starting glycals as leaving groups under neutral conditions have been developed. General features of the reactions are described as well as applications in synthesis and extensions of the basic processes.

Substitution-with-Allylic-Rearrangement Reactions of Glycal Derivatives

Tri-O-acetyl-D-glucal undergoes complete reaction with alcohols in benzene solution in the presence of boron trifluoride to give 4,6-di-O-acetyl-2,3-dideoxy-D-erythro-hex-2-enopyranosides. The α-anomers predominate (ca. 90%), and the method can be used to prepare the known crystalline ethyl α-glucoside easily and in greatly improved yield. Other alkyl glycosides have been prepared similarly, and the procedure has afforded means of obtaining the cholesteryl analogue and the disaccharide derivative 6-O-(4,6-di-O-acetyl-2,3-dideoxy-α-D-erythro-hex-2-enopyranosyl)-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose. Tri-O-acetyl-D-glucal again gave the 2,3-unsaturated glycosides on treatment with acetals in the presence of boron trifluoride; no evidence was obtained for the formation of branched-chain products produced by additions to the double bond.

R. J. Ferrier

Papers

Unsaturated carbohydrates. Part IX. Synthesis of 2,3-dideoxy-α-D-erythro-hex-2-enopyranosides from tri-O-acetyl-D-glucal