A Convenient Approach for Access to Both Carbapentofuranoses and Carbahexopyranoses. Stereocontrolled Synthesis of Enantiopure Carba-d-ribofuranoses, Carba-d-arabinofuranoses and Carba-l-gulopyranose

Abstract

A new approach to carbasugars in enantiomerically pure form is reported. The key step involves ringclosing metathesis of dienols 6 derived from a (R)-(+)-glyceraldehyde derivative 4 to form the substituted cyclopentenol 9 and cyclohexenol 34a. Stereocontrolled addition of hydroxyl groups followed by conversion of the ketal unit to hydroxymethyl group in these intermediates led to carbapentoses and -hexoses. Stereoselectivity during introduction of hydroxyl groups arises through the steric hindrance posed by the allylic substituents. A remarkable feature of the present approach is the accessibility of both D-and L-series of carbapentoses as illustrated by the synthesis of β-D-and β-L-carbaribofuranoses 17 and 20, respectively. Carba-R-D-ribofuranose 25, the biosynthetic intermediate to the antibiotic aristeromycin, has also been synthesized from the same cyclopentenol 9. Functional group manipulation in the cyclopentenol 9a also enabled access to carbaarabinofuranose 32. The present synthetic strategy can be extended for the synthesis of carbahexopyranose, as illustrated by the synthesis of carba-β-Lgulopyranose 40b.

Synthesis of novel N-cyclopentenyl-lactams using the Aubé reaction

“…In addition, crystals of the triol (±)- 12 were obtained and single crystal X-ray analysis further established the assigned structure without any ambiguity, as shown in Fig. 2 and Supporting Information File 1 [46–47]. The synthesized trihydroxylated amides (±)- 11 –(±)- 15 can be considered as mimics of 1,2-carbocyclic nucleosides due to close structural resemblance with that of molecules documented in the literature [29–30].…”

A simple approach to the construction of the core structure present in bielschowskysin and hippolachnin A

“…Infrared spectra were recorded as thin films. (10) A solution of the known hydroxy compound 8 8 (390 mg, 1.55 mmol) in anhydrous THF (10 mL) was added to a stirred suspension of sodium hydride (112 mg, 2.32 mmol, 50% suspension in oil) in anhydrous THF (5 mL) at 0 • C. After 15 min, allyl bromide (0.27 mL, 3.09 mmol) was added to it at 0 • C. The reaction mixture was stirred at rt for 2 h and then quenched with saturated aqueous ammonium chloride solution (5 mL). The reaction mixture was extracted with diethyl ether (3 × 10 mL).…”

Synthesis of Carbasugars Based on Ring Closing Metathesis: 2000-2006

“…More recently, Ghosh et al have described a stereodivergent approach to carbasugars that has allowed the preparation of carba--Dand carba--D-arabinofuranoses (36) and (37), respectively (see Schemes 4 and 5) [45]. Their general approach, also useful for the preparation of carba-D-ribofuranoses and carba-L-gulopyranoses (vide infra), is outlined in Scheme 4.…”

“…The previously mentioned approach by Ghosh and coworkers (Scheme 4) [45] was also implemented for the synthesis of 5a-carba--Lgulopyranose pentaacetate (154) as shown in Scheme 20. Reaction of aldehyde (144) with allyl zinc afforded a diastereomeric mixture of alcohols (145).…”