NOVELTY - Preparing (S)-2-(3-tert-butyl-ureido)-3,3-dimethyl-butyric acid (2) or its salt, comprises reacting (S)-2-amino-3,3-dimethyl-butyric acid ester derivative (5) or its salt with a reagent and a tert-butyl amine or its derivative to give (S)-2-(3,3-dimethyl-butyrylamino)-3,3-dimethyl-butyric acid derivative (6); and optionally converting (6) to (2) or its salt.    USE - The process is useful for preparing (S)-(tert-butyl-ureido)-dimethyl-butyric acid, which is used to prepare boceprevir or its salts (claimed), which is useful for treating hepatitis C virus infections. No biological data given.    ADVANTAGE - The process is: environmentally friendly, economical and provides (S)-(tert-butyl-ureido)-dimethyl-butyric acid with shorter reaction time and better purity and yield; and industrially scalable.    DETAILED DESCRIPTION - Preparing (S)-2-(3-tert-butyl-ureido)-3,3-dimethyl-butyric acid (2) or its salt, comprises reacting (S)-2-amino-3,3-dimethyl-butyric acid ester derivative of formula (CH3-C(CH3)2-C(NH2)-C(=O)-O-R1) (5) or its salt with a reagent and a tert-butyl amine or its derivative to give (S)-2-(3,3-dimethyl-butyrylamino)-3,3-dimethyl-butyric acid derivative of formula (CH3-C(CH3)2-NH-C(=O)-NH-CH(C(CH3)3)-C(=O)-OR1) (6); and optionally converting (6) to (2) or its salt.R1 = H, alkyl (optionally substituted) or aryl.    INDEPENDENT CLAIMS are also included for:    (1) preparation of 3-amino-3-cyclobutylmethyl-2-hydroxy-propionamide (3) or its salt, comprising (a) reacting N-protected 2-amino-malonic acid derivative of formula (R2-O-C(O)-C(NH-P1)-C(O)-O-R3) (7) with a halomethyl-cyclobutane compound of formula (8) to give N-protected-2-amino-2-cyclobutylmethyl-malonic acid compound of formula (9), (b) reacting (9) with a reagent to give 2-amino-3-cyclobutyl-propionic acid (10) or its salt, (c) converting (10) or its salt to 2-amino-3-cyclobutyl-propionic acid derivative of formula (11), (d) protecting (11) to give N-protected 2-amino-3-cyclobutyl-propionic acid derivative of formula (12), (e) reducing (12) to provide N-protected 2-amino-3-cyclobutyl-propionaldehyde of formula (13), (f) reacting (13) with 2-hydroxy-2-methyl-propionitrile to provide N-protected 3-amino-4-cyclobutyl-2-hydroxy-butyronitrile compound of formula (14), (g) converting (14) to provide N-protected 3-amino-4-cyclobutyl-2-hydroxy-butyramide compound of formula (15), and (h) deprotecting (15) to provide (3) or its salt;    (2) preparation of 2-amino-3-cyclobutyl-propionic acid (10) comprising the steps (a) and (b) as above per se;    (3) preparation of (6,6-dimethyl-3-aza-bicyclo(3.1.0)hex-2-yl)-methanol (16) or its stereoisomers, comprising reacting (a1) (1S,3S)-3-(2,2-dichloro-vinyl)-2,2-dimethyl-cyclopropane carboxylic acid derivative of formula (17) with ammonia reagent in a solvent to provide (1S,3S)-3-(2,2-dichloro-vinyl)-2,2-dimethyl-cyclopropanecarboxylic acid amide (18), (b1) converting (18) to 4-(1-chloro-meth-(Z)-ylidene)-6,6-dimethyl-3-aza-bicyclo(3.1.0)hexan-2-one (19), (c1) converting (19) to 4-chloromethyl-6,6-dimethyl-3-aza-bicyclo(3.1.0)hexan-2-one (20), (d1) converting (20) to 6,6-dimethyl-4-oxo-3-aza-bicyclo(3.1.0)hex-2-ylmethyl ester derivative of formula (21), (e1) converting (21) to 4-hydroxymethyl-6,6-dimethyl-3-aza-bicyclo(3.1.0)hexan-2-one (22), and (f1) reducing (22) to (16);    (4) preparation of 4-(1-chloro-meth-(Z)-ylidene)-6,6-dimethyl-3-aza-bicyclo(3.1.0)hexan-2-one (19) or its stereoisomers, comprising the steps (a1) and (b1) as above per se;    (5) preparation of 6,6-dimethyl-3-aza-bicyclo(3.1.0)hexane-2-carboxylic acid derivative of formula (4) or its stereoisomers or salts, comprising either (a2) reacting (16) with nitrogen protecting agent to provide N-protected alcohol of formula (23), (b2) oxidizing (23) to an acid of formula (24), (c2) esterifying (24) to provide an ester of formula (25), (d2) epimerizing (25) to provide acid of formula (26), and (e2) deprotecting and esterifying (26) to provide (4) or its stereoisomers or salts, or the step (a2) as above per se, oxidizing (23) to an aldehyde of formula (27), epimerizing (27) to provide N-protected (1R,2S,5S)-6,6-Dimethyl-3-aza-bicyclo(3.1.0)hexane-2-carbaldehyde of formula (28), oxidizing (28) to give (26) and the step (e2) as above per se, or oxidizing (28) to provide (26) and the step (e2) as above per se, or converting (19) to (16), reacting (16) with nitrogen protecting agent to give (23), oxidizing (23) to provide (27), epimerizing (27) to provide (28), (a4) oxidizing (28) to provide ester of formula (29), and (b4) deprotecting (29) to provide (4), or the steps (a4) and (b4) as above per se, or the step (a1) as above per se, reacting (18) with a reducing agent in a solvent to provide C-((1S,3S)-3-(2,2-dichloro-vinyl)-2,2-dimethyl-cyclopropyl)-methylamine (30), converting (30) to an amino protected compound of formula (31), converting (31) to a chloro compound of formula (32), oxidizing (32) to (27), epimerizing (27) to (28), oxidizing (28) to (26) and the step (e2) as above per se, or the steps of converting (30) to (31), (31) to (32), (32) to (27), (27) to (28), (28) to (26) and (26) to (4) as above per se;    (6) epimerization of aldehyde (27) to provide (28);    (7) preparation of C-((1S,3S)-3-(2,2-dichloro-vinyl)-2,2-dimethyl-cyclopropyl)-methylamine (30) or its stereoisomers or salts, comprising the step (a1) as above per se and reacting (18) with reducing agent in solvent to provide (30);    (8) oxidation of the chloro compound (32) to the aldehyde (27);    (9) N-protected-2-amino-2-cyclobutylmethyl-malonic acid compound (9), 4-(1-chloro-meth-(Z)-ylidene)-6,6-dimethyl-3-aza-bicyclo(3.1.0)hexan-2-one (19), 4-chloromethyl-6,6-dimethyl-3-aza-bicyclo(3.1.0)hexan-2-one (20), the aldehyde (27), N-protected (1R,2S,5S)-6,6-Dimethyl-3-aza-bicyclo(3.1.0)hexane-2-carbaldehyde (28), C-((1S,3S)-3-(2,2-dichloro-vinyl)-2,2-dimethyl-cyclopropyl)-methylamine (30), and the chloro compound (32); and    (10) composition comprising boceprevir or its salts prepared from (2), (3) and (4) or their stereoisomers or salts, and at least one excipient, carrier or diluent.    R2, R3, R4 = alkyl;    P1 = amine protecting group, preferably acetyl;    Y1 = halo;    R5 = OH, Br, Cl, I, or OR6;    R6, R = 1-8C alkyl; and    R7 = alkyl or aryl.