Lactone synthon

From Bromodeoxy/Tosyloxy Aldonolactones to Other Lactone Synthons... 

With the Corey lactone four of the stereocenters (8,9,11,12) are defined in the lactone synthon, although there could be a slight concern with the integrity of the stereocenter at position 12 because as an aldehyde intermediate there is some chance of epimerization at that center via its enol. The main problem with this approach is the control of the stereocenter at position 15, which has to be introduced late into the process. Inevitably, there is some diastereoisomer formed, which can be... 

The optically pure y-lactone synthons 93 (R=Bn or Tr) were obtained from Z-glutamic acid and were used as chiral templates in three different asymmetric sequences. In paths a and b, a 1,3-asymmetric induction from the y to the a-lactone position was performed in two different manners, whereas in path cal, 2-asymmetric induction from the y to the 3-lactone position was described. 

Compactin rely on a Diels-Alder strategy. An intermolecular version has diene (468) as the key synthon and suffers from a poor yield in the final demethylation step whereas an intramolecular approach using the aldehyde (469), derived from tri-O-acetyl-D-glucal, as the lactone synthon suffers from no such drawback at the... 

The arrangement of functional groups as well as the erythro configuration of the latent diol makes carbonate 517 an excellent candidate as a compactin lactone synthon (99) and it has in fact been used in the synthesis of both compactin (97) and mevinolin (98) (Scheme 75) [112]. 

In model studies related to the synthesis of compactin (97) and mevinolin (98), the upper-half lactone moiety was constructed from 550 starting with an oxirane ring-opening reaction by vinyl Grignard reagent (Scheme 81) [136]. lodocarbonation of 560 followed by hydrolysis and ketalization affords isomerically pure acetonide 562, the compactin lactone synthon. 

The preparation of the octa-Q-benzoyl-aldobiononitriles of cellobiose, gentiobiose, lactose, and maltose from the unprotected oximes has been effected by treatment with benzoyl chloride in pyridine at SO C. Reaction of melibiononitrile perbenzoate with methanolic ammonia yielded the 1,1-dibenzamido-derivative (37) as the major product, isolated in 38% yield.The erythro- and threo-cyanohvdrins (38) were obtained in a 4 1 ratio from 2,3-Q-isopropylidene-D-glyceraldehyde on reaction with trimethylsilyl cyanide, and were converted to the four carbon lactone synthons (39). The chiral hexane-1,6-dinitrile (40) has been synthesized CHjOH... 

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