Introduction: During instrumentation smear layer formation occurs on dentinal wall and for a successful root canal its removal is necessary. Aim of the study was to compare effect of 17% EDTA, MTAD & 18%Etidronic acid (HEBP) + 5% NaOCl, irrigating solutions on smear layer removal and penetrability of AH Plus sealer into dentinal tubules using scanning electron microscopy (SEM). Material and methods: Sixty single rooted mandibular premolars, were divided into three groups (n=20).Group-I 17% EDTA, Group-II MTAD, Group-III 18%Etidronic acid+ 5% NaOCl. The final rinse was done by 5ml of solution for 2 minutes. Ten samples from each group were evaluated at middle and apical thirds for smear layer removal using SEM. Remaining ten samples of each group were obturated with gutta-percha & AH PLUS sealer and evaluated at 5mm above from the root apex for sealer penetration using SEM. Results: At middle 3rd no difference in smear layer removal was seen between Group-I and Group-II For apical 3rd Group-II showed better smear layer removal than Group-I and Group-III. Thus both in middle and apical thirds MTAD showed better smear layer removal. For mean sealer penetration Group-II showed a highest depth of sealer penetration i.e, 231.37±18.12µm followed by Group-I 154.95±22.53µm and Group-III 125.99±17.39µm Conclusion: MTAD is effective in smear layer removal from both middle and apical thirds. Maximum depth of sealer penetration was seen in MTAD group followed by EDTA group and least in Etidronic acid group.

First stereoselective total synthesis of (+)-diaportinol, (À )-peniisocoumarin H and (+)-& (À )-desmethyldiaportinol is demonstrated and their absolute stereochemistry was revised accordingly. A convergent approach has been developed that uses L-malic acid as chiral synthons for the synthesis of 2, and D-malic acid for 1 and 3. O,O-Dimethylorsellinic acid ester was prepared and coupled with Weinreb amide 6 or 6D via lateral lithiation carbonylation and a subsequent base catalyzed cyclization provided the isochromenone moiety and a selective deprotection was achieved using BBr 3 .

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