Q2. What are the popular functions of tetrazoles?
They can serve as bioisosteres of carboxylic acids,1,2 as precursors of nitrogen-containing heterocycles, and as lipophilic spacers in pharmaceuticals.
Q3. What is the mechanism of formation of tetrazole 6?
Formation of exo-cyanoethylidene 5 is expected to be kinetically favored due to an attack from the sterically less hindered convex side of bicyclic 8.
Q4. What is the common side reaction of cyanoethylidene compounds?
22–24 Myers et al. showed that cyanoethylidenecompounds of mannose, glucose, and galactose can be converted to anomeric cyanides under acid promotion without an exogenous cyanide source.
Q5. What is the reaction reaction for cyanoethylidene?
Anomeric deprotection of 10 by treatment with hydrazinium acetate for 3 h at 50 C and subsequent acetylation with pyridine/Ac2O led to the formation of 11 as a mixture of anomers (a:b = 1:2.9) in 41% yield over 2 steps.
Q6. What is the reaction reaction for tetrazole?
Proper spatial orientation of azido and cyano groups within endo-cyanoethylidene 9 obviously leads to a fast irreversible intramolecular cycloaddition forming tetrazole 6.
Q7. What is the role of carbohydrates in the formation of tetrazoles?
Their results highlight the capability of carbohydrates to act as scaffolds for the precise positioning of functional groups productive for a specificchemical reaction.
Q8. What is the common method for the preparation of tetrazoles?
A potentially useful method for the preparation of 1,5-disubstituted tetrazoles is the [2+3] cycloaddition of organic azides to nitriles.
Q9. How did the authors react with tetrazole 6?
To isolate and characterize cyanoethylidene intermediate 5, the authors reacted 3 with TMSCN (5 equiv) and catalytic amounts of Lewis acid (0.2 equiv SnCl4) at room temperature.
Q10. how did i obtain the b-pyranose 3?
When using 60% formic acid for the cleavage of the isopropylidene protecting groups of 1, the authors observed the formation of two different formylated side products, which could subsequently be converted with NaOMe/MeOH to the completely deprotected 3-azido3-deoxy-D-allose 2 existing predominantly as b-pyra-O OHHON3 OHOAcON OOAcO N N NOO ON3 O Oa or b c OH1 267e OHON OOHO N N NScheme 1.
Q11. How did the authors obtain the peracetylated allopyranose derivative 3?
Starting from 3-azido-3-deoxy-1,2:5,6-di-O-isopropylidene-a-D-allofuranose 126 the authors obtained the peracetylated allopyranose derivative 3 using two different pathways.
Q12. What is the way to get a b-pyranose?
Treatment with acetic anhydride in pyridine afforded peracetylated b-pyranose 3 in 91% yield over 3 steps besides small amounts of the corresponding a- and bfuranose and a-pyranose forms.
Q13. What is the yield of the endo-cyanoethylidene derivative?
Since the endo-cyanoethylidene derivative 21 could be isolated in the allofuranose case, the authors conclude thatHOMe OOON3 OHOMe16 a7, 78%.
Q14. What is the reaction of organic azides to nitriles?
In the course of their investigations toward the Lewis-acid promoted synthesis of glycosyl cyanides, the authors now observed an unexpected side reaction leading for the first time to complex bridged tetracyclic ring systems via 1,3-dipolar cycloaddition of intermediate cyanoethylidene derivatives of 3-azidoallose even at room temperature.
Q15. What is the chemical structure of the sugar diamino acids?
In the course of their program directed at the synthesis of sugar diamino acids (SDAs) as building blocks of oligosaccharide mimetics,25 the authors were interested in glycosyl cyanide 4 of 3-azido-3-deoxy-D-allopyranose (Scheme 1).
Q16. How many mpounds of pyranose were used?
Tetrazole 6 shows a 13C NMRO OAcAcON3 OAcOAc O OAc AcON3 OAcCNd354OAcON3 OOAcOCNdMeOH, 2 h; (b) 2 M HCl, 6 h; (c) Ac2O, pyr, overnight, 91% [(a) + (c)], e) NaOMe, MeOH, 14 h, 84%.mpounds 5 and 6.